Individual Phenolic Acids Research Articles

Enhancement of antioxidant activity and bioactive compound contents in yellow soybean by plant-extract-based products

Polyphenols present in different plant cell organelles increase the resistance of plants to various types of environmental stresses. We investigated the possibility of increasing the content of bioactive compounds in the seed of yellow soybean variety Laura. The soybean was treated during vegetation with five products based on plant extracts, on the assumption of enrichment of plants with various nutrients. Soybean flour extracts were screened spectrophotometrically for total phenolic content and antioxidant activity. The antioxidant activity was evaluated using three methods. The content of phenolic acids was determined by HPLC, and the raw protein content was estimated by the Kjeldahl method. Depending on the treatment, variations in the quantity of individual phenolic acids with up to 90% higher concentration as compared to the control were observed. Controlled usage of certain plant extracts can increase the concentration of the target group of bioactive compounds in the samples. The synergistic effect of proteins and phenolic compounds on the antioxidant activity of extracts was detected. The results of this study are not only important from the aspect of plant resistance to various types of stress, but also when considering soybean as a functional food. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 31018, Grant no. 31037, Grant no. 37021 and Grant no. 172015]

Comparative studies on ACE inhibition, degree of hydrolysis, antioxidant property and phenolic acid composition of hydrolysates derived from simulated in vitro gastrointestinal proteolysis of three thermally treated legumes

Three phenolic-rich legume varieties underwent in vitro simulated gastrointestinal proteolytic digestion after a wide range of thermal treatments. Total phenolic content (TPC), DPPH free radical scavenging activity (DPPH), degree of hydrolysis (DH), angiotensin-I converting enzyme (ACE) inhibitory activity of hydrolysates showed significant differences among thermal treatments. TPC values of hydrolysates were significantly (p < 0.05) higher than their corresponding undigested counterparts. The DPPH values were significantly (p < 0.05) lower than their corresponding undigested counterparts. DH had no correlations (p > 0.05) with ACE inhibitory activity for all three legumes. When compared with undigested legumes, the simulated gastrointestinal tract proteolytic digestion induced marked changes not only in the content, but also in the type of individual free phenolic acids. The present study clearly implied that literature data of phenolics and their potential health benefits derived from undigested legumes cannot accurately represent the real situations after the digestion process.

Metabolic changes induced by manganese in chamomile

Manganese (Mn) uptake and toxicity in chamomile (Matricaria chamomilla) and changes of phenolic metabolites in plants grown in the soil (1000 μM Mn2+) or hydroponic culture (100 or 1000 μM Mn2+) were studied. Under soil cultivation, Mn excess reduced growth and induced symptoms of oxidative stress (including total ROS, hydroxyl radical and lipid peroxidation as detected by fluorescence microscopy), concomitantly with depletion of non-protein thiols and ascorbic acid. Total soluble phenols and individual phenolic acids were rather depleted (p-coumaric, chlorogenic, and protocatechuic acids) or unaltered (vanillic and caffeic acids). Shoot Mn content reached 2806 μg/g DW with BAF 51.0 in the soil culture. In hydroponics, tetraploid plants contained less Mn in both shoots and roots than diploid ones with bioaccumulation factor and translocation factor (diploid/tetraploid) 57.1/37.9 and 0.39/0.32 in 1000 μM Mn treatment. Plants cultured in hydroponics revealed stimulation of some phenolic acids, mainly chlorogenic acid in the shoots and p-hydroxybenzoic and vanillic acids in the roots (more extensively in tetraploid ones which contained less Mn). Data indicate that excessive Mn accumulation has negative impact not only on the growth but also on phenolic metabolites in young plants mainly. Detailed comparison of the observed metabolic changes with limited literature focused on Mn physiology is provided as well.

In vitro evaluation of the bioaccessibility of phenolic acids in different whole wheats as potential prebiotics

Whole wheat has often been associated with health benefits conveyed by the phenolic acids made accessible in the colon which enable the modulation of the gut microbiota. In the present study, the bioaccessibility of nine individual phenolic acids present in different wheat varieties was evaluated by in vitro gastrointestinal digestion and colonic fermentation. Most of the individual phenolic acids in the complex wheat matrix had a higher bioaccessibility after the in vitro digestion step (average 57.7%–82.1%), than after in vitro colonic fermentation (21.9%–47.5%). However, the contents of cinnamic, caffeic, and protocatechuic acids in several wheat varieties were higher in the intestinal digesta than in the undigested samples, and the content of erucic acid was higher in fermented slurry than in the intestinal digesta. The bioaccessibility of certain phenolic compounds also varied significantly between different wheat varieties. Other compounds in wheat interfered with the release of phenolic acids during digestion and fermentation. The contents of phenolic acids remaining in the digesta were significantly correlated with the abundance of at least one bacterial genus during colonic fermentation. This suggests that both concentrations and food composition should be considered when selecting whole wheat with associated phenolic acids for use as potential prebiotics.

Development of HP-TLC method for rapid quantification of sugars, catechins, phenolic acids and saponins to assess Yam (Dioscorea spp.) tuber flour quality

AbstractEight yam species (Dioscorea spp.) represented by 522 accessions (landraces and hybrids) were analysed for the individual sugars, catechins, phenolic acids and saponins contents of their tuber flours. Maltose, sucrose, glucose and fructose were quantified. Reducing sugars mean values were highly variable within species and ranged from 0.16%dry weight (DW) (SD ± 0.12) in D. dumetorum to 3.15%DW (±2.49) in D. esculenta. Maltose was detected only in D. esculenta. Chlorogenic acid, gallic acid and other phenolic acids ranged from 4.33 mg/g DW in D. bulbifera to 4.87 mg/g in D. alata and 9.55 mg/g in D. nummularia but were not detected in other species. Catechins (epicatechin and catechin) were highest in D. bulbifera bulbils (25.18 mg/g) and tubers (6.96 mg/g), and lowest in D. esculenta (0.32 mg/g). Their content is significantly correlated with dark flour colour and they most likely contribute to the oxidation of tuber flesh. Saponins (dioscin and gracillin) were quantified in only two species: D. cayenensis (5.94 mg/g, SD ± 3.78) and D. esculenta (3.74 mg/g, SD ± 3.72). Varietal selection may tend to reduce sugars levels and increase secondary metabolites with bioactive properties. HP-TLC is a suitable technique for the rapid quantification of compounds related to yam tuber flour quality.

Influence of the vegetation period on sea fennel, Crithmum maritimum L. (Apiaceae), phenolic composition, antioxidant and anticholinesterase activities

Since ancient times Crithmum maritimum L. (Apiaceae) or sea fennel, has been used in culinary practices and in folk medicine, but in the last few years it has become a rediscovered star of coastal cuisine. In this study, chemical composition (total phenolics, flavonoids, non-flavonoids, individual phenolic acids), antioxidant (FRAP, ORAC, DPPH, Briggs-Rauscher oscillating reaction) and cholinesterase (AChE, BuChE) inhibitory activities of the sea fennel samples collected in different seasons during a one-year vegetation period were investigated. The obtained results point out the great influence of the plant vegetation period on content of phenolics and consequently on plant biological activity. The sample collected before the flowering stage (in April) was, in most cases, superior in comparison to other extracts which opens a new realm of possibilities of its applications in different products and industries.

The maturity degree, phenolic compounds and antioxidant activity of Eureka lemon [Citrus limon (L.) Burm. f.]: A negative correlation between total phenolic content, antioxidant capacity and soluble solid content

Lemon fruits are well-known for their economic, nutrition and health values. In this study, the maturity degree, phenolic compounds and antioxidant capacity of Eureka lemon [Citrus limon (L.) Burm. f.] fruits harvested at different months of the year were investigated. We found that the fruits harvested in November outperformed others in terms of weight, total sugar and soluble solid content (SSC). The ρ-coumaric acid, ferulic acid, eriocitrin and hesperidin were the predominant phenolic compounds in lemon fruits. The highest total phenolic content (TPC, 3.49 ± 0.05 mg GAE g−1 FW), total flavonoid content (TFC, 1.46 ± 0.05 mg RE g−1 FW), sum of individual phenolic acids content (269.36 μg g−1 FW) and their antioxidant potency composite (APC) index (100.00%) were found in the pulps of April fruits. The maximum of sum of individual flavonoids content (3098.42 μg g−1 FW) exhibited in August. For the peels, the highest TFC (6.35 ± 0.24 mg RE g−1 FW) and APC (95.14%) appeared in April fruits, while the highest TPC (7.96 ± 0.17 mg GAE g−1 FW) and sum of individual flavonoids content (9003.91 μg g−1 FW) occurred in the August. However, the maximum of sum of individual phenolic acids content (769.28 μg g−1 FW) was detected in June fruits. We also found that soluble solid content (SSC) of the pulps of lemon fruits were negatively correlated with their TPC and APC. TPC also decreased with the increase in SSC of peels. Most importantly, our study indicated that the contents of phenolic compounds and antioxidant activity of lemon fruits varied significantly with their maturity degrees depending on different harvest time, and this information is essential for a better use of different lemons fruits resources.

The cytotoxic effect of artificially digested buckwheat products on HT-29 colon cancer cells

Recently Europeans are showing a growing interest in healthy foods. In light of this fact, the aim of our study was to evaluate the effect of buckwheat products (groats, hull, and bran) after in vitro digestion in an artificial gastrointestinal tract on the inhibition of HT-29 cancer cell proliferation. We investigated the content of individual flavonoids, phenolic acids, amino acids, and thiamine in these buckwheat products. The MTT (thiazolyl blue tetrazolium bromide) assay was used to evaluate the viability and metabolic activity of the colon cancer cells. We found significant (p < 0.05) negative correlations between HT-29 cell growth and the levels of catechin, quercetin, serine, proline, glycine, histidine and arginine in buckwheat samples after digestion. Our results highlight that buckwheat by-products are a rich source of bioactive substances such as: quercetin, catechin, serine, proline, glycine, histidine, and arginine. Therefore, buckwheat can be used as an additive in pro-health foods.

Effects of postharvest UV-C irradiation on phenolic acids, flavonoids, and key phenylpropanoid pathway genes in tomato fruit

Abstract The possibility of increasing the content of phenolic acids and flavonoids, and inducing the key phenylpropanoid pathway genes in tomato fruit by postharvest UV-C irradiation was assessed. Mature-green tomato fruit were irradiated with UV-C at 4 kJ m−2 and stored in the dark at 13 °C and 95% RH. UV-C irradiation was effective in increasing the total phenolics content and individual phenolic acids and flavonoids, including cafferic acid, p-coumaric acid, trans-ferulic acid, chlorogenic acid, gallic acid, protocatechuic acid, rutin and quercetin. UV-C treatment also induced expression of genes coding for key enzymes in the phenylpropanoid pathway, including PAL, C4H, 4CL, CHS, CHI, F3H and FLS, and enhanced the activities of PAL, C4H, 4CL, CHS and CHI during storage, which in agreement with a corresponding increase in phenolic compounds content. UV-C irradiation resulted in an increase of the content of phenolic acids and flavonoids in tomato fruit during storage.

The impact of high-power ultrasound and microwave on the phenolic acid profile and antioxidant activity of the extract from yellow soybean seeds

The aim of the study was to investigate and compare several extraction protocols like 1) high-power ultrasound probe assisted solvent extraction; 2) microwave assisted solvent extraction; 3) direct acid hydrolysis; 4) direct alkali hydrolysis, and 5) two step extraction consisting of ultrasound or microwave assisted solvent extraction followed by alkaline and acid hydrolysis in terms of efficiency of the extraction of phenolic acids from the yellow soybean seed variety Laura. These extracts were screened for their total phenol content (TPC), and for their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH) assay, as well as on content of some individual phenolic acids. It appeared that the acetone containing mixtures gave much higher TPC than methanol containing ones, but the presence of acid in the methanol solvent significantly improved the extraction of phenolic compounds. To further improve the extraction, an ultrasound lab-scale probe at 20 kHz was used, with 15 and 30% of the maximum amplitude, and the extraction time was varied from 2 to 15 min. Microwave assisted extraction was performed varying the temperature from 55 to 85 °C, microwave power from 25 to 100 W and extraction time from 2 to 10 min. Changes in the content of six phenolic acids were examined: gallic, trans-cinnamic, chlorogenic, caffeic, p-coumaric and ferulic acid. The separation and quantification of phenolic acids was accomplished by high-performance liquid chromatography-diode array detection (DAD) procedure. The results suggested that microwaves contributed to more efficient extraction of phenolic acids from the seed of yellow soybean. The amount of phenolic acids varied from 65.52 μg/g of dry matter (d.m.) for caffeic acid, to 581.84 μg/g d.m. for p-coumaric acid. Both, ultrasound and microwaves contributed to more efficient extraction of total phenol compounds and enhanced antioxidant activity of soybean seed extracts. TPC varied from 12.48 to 18.77 mg GAE/g d.m. and antioxidant activity varied from 244.58 to 345.21 μmol TROLOX eq/g d.m.

Determination of phenolic acids in extra virgin olive oil using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

Phenolic acids represent one third of the total phenolic compounds in extra virgin olive oil (EVOO) and contribute greatly to the biological and sensory properties of EVOO. In the present research, an analytical method based on supercritical fluid chromatography coupled with single quadrupole mass spectrometry (SFC-MS) was developed for the analysis of phenolic acids in EVOOs. The chromatographic and MS conditions were optimized in terms of selectivity, peak shape and sensitivity. Satisfactory separation of 12 phenolic acids was achieved within 20 min on a Platisil CN column (250 mm × 4.6 mm, 5 μm) using 7% (v/v) water and 0.5% (v/v) formic acid in MeOH as mobile phase additives at the backpressure of 140 bar and temperature of 60 °C. The developed method was validated by evaluating the linearity, sensitivity, repeatability, intermediate precision and accuracy. The limits of detection (LODs) and limits of quantification (LOQs) of the SFC-MS method for phenolic acids ranged from 0.03 to 5.00 μg/mL and 0.08 to 15.0 μg/mL, respectively. The relative standard deviations (RSDs) for intraday and interday precision were lower than 9.91% and the recoveries ranged from 80.2 to 117% and 80.9 to 118% for low-level and high-level concentrations of standards spiked in olive oil, respectively. Compared to an HPLC method, the SFC method was about three times faster and provided better selectivity. Finally, the SFC-MS method was successfully employed for the quantitative analysis of phenolic acids in EVOOs. Differences in individual and total phenolic acid contents were observed between six varieties.

Role of Phenolic Acids from the Rhizosphere Soils of Panax notoginseng as a Double-Edge Sword in the Occurrence of Root-Rot Disease.

Chemical agents in the rhizosphere soils of plants might have an influence on root-rot disease, which therefore might reveal the mechanism of root rot in Panax notoginseng (P. notoginseng). With this hypothesis the alterations of phenolic acids (PAs) in the rhizosphere soils of P. notoginseng after pathogen infection were determined. The effects of PAs on the growth of Fusarium oxysporum (F. oxysporum), a fungal pathogenic factor for P. notoginseng, as well as production of fusaric acid, a wilting agent for the plants, were also examined. The results indicate the presence of five PAs (ferulic acid, syringic acid, p-hydroxybenzoic acid, p-coumaric acid, and vanillic acid) in the rhizosphere soils of P. notoginseng, whose contents in the rhizosphere soils of healthy plants are higher than those of the diseased ones. Further we found that individual PA could inhibit the mycelium growth and spore production of F. oxysporum, but stimulate fusaric acid production as well, disclosing the double-edge sword role of PAs in the occurrence of root rot of P. notoginseng and paving the way for the intervention of P. notoginseng root rot via balancing PAs.

Characterization of dried chokeberry fruit extract and its chronic effects on blood pressure and oxidative stress in spontaneously hypertensive rats

The potential beneficial effects of chronic consumption of dried chokeberry fruit extract (DCE) were evaluated in the present in vivo study. The study concentrates on haemodynamic parameters, lipid profile and oxidative stress in spontaneously hypertensive rats. DCE was characterized by HPLC/DAD method and individual anthocyanins, phenolic acids, and flavonoids were determined. Four week administration of DCE, rich in polyphenols, especially anthocyanins, significantly reduced systolic (P < 0.05), pulse pressure (P < 0.05) compared to control group, probably via significantly increased diuresis (P < 0.05). Significant decrease of plasma and erythrocytes TBARS was also found in the treated group. DCE consumption reduced lipid peroxidation through improving plasma FRAP reducing (P < 0.01). The activity of SOD in the treated group had been significantly lower (P < 0.01) compared to the control group. These results suggest that DCE could exert beneficial effects on cardiovascular health and has a potential as a nutritional supplement in arterial hypertension.

Occurrence of targeted nutrients and potentially bioactive compounds during in vitro digestion of wheat spaghetti

In vitro digestates of spaghetti, made from durum or common wheat and dried at low or high temperature, were assessed for the occurrence of soluble sugars, gluten exorphins and phenolic acids. Digestates were also studied for coeliac toxicity, antioxidant properties, anti-glycation activity and capacity to inhibit amylolytic enzymes. Level of released sugars depended on the applied drying cycle. The exorphins C5 and A5 were found in all gastric or intestinal digestates, respectively. The fate of individual phenolic acids during cooking and digestion was not unidirectional, but the total content of phenolic acids increased as long as the digestion proceeded. Intestinal digestates presented the highest antioxidant capacity, while they kept coeliac toxicity. Gastric digestates showed potential inhibitory effects on α-amylase and α-glucosidase. These findings indicate that dried pasta, in addition to being a source of nutrients, delivers bioactive compounds and biological features being modulated by heat treatment and digestion process.

Sonchus oleraceus Residue Improves Nutritive and Health-Promoting Value of Common Bean ( Phaseolus vulgaris L.): A Metabolic Study.

This study was conducted to evaluate the use of the phenolic-rich Sonchus oleraceus residue as an environmentally safe approach to induce the nutritive and health-promoting values of common bean ( Phaseolus vulgaris L. cv. Bronco). S. oleraceus shoot residue, at rates of 150 and 300 g m-2, has improved soil fertility via accumulation of soil macronutrients, organic matter, organic carbon, and total phenolics. The growth and yield of bean were significantly increased. Moreover, chemical composition of the treated seeds was significantly altered, whereas higher levels of total antioxidant capacity, proteins, carbohydrates, and most of the individual phenolic acids, flavonoids, vitamins, essential amino acids, and unsaturated fatty acids were recorded. Interestingly, a concentration dependent effect was also observed, for instance, a lower saturated-to-unsaturated fatty acid ratio was only observed in the case of the lower residue rate. These findings recommend the use of S. oleraceus in organic farming of bean to enhance the health benefits of the produced seeds.

Extraction of phenolic compounds with antioxidant potential from coconut (Cocos nucifera L.) testa and identification of phenolic acids and flavonoids using UPLC coupled with TQD-MS/MS

Coconut testa, a brown skin covering of a coconut endosperm, is a rich source of phenolics. It is one of the by-products obtained in the coconut processing industries and currently underutilized despite being rich in phenolic compounds. A study was conducted to identify the suitable solvent system for maximum extractability of total phenolic content (TPC) and total flavonoid content (TFC) with antioxidant potential from the testa. Individual phenolic acids and flavonoids of different solvent extracts were also determined using UPLC-H class coupled with TQD-MS/MS. The TPC and TFC ranged from 4.9 to 167 mg GAE/g and 8.84–115 mg QE/g defatted testa, respectively; significant differences were observed for various solvent systems studied. Acidification of solvents significantly increased the extractability of TPC and reduced the extractability of TFC. A total of 28 phenolics comprising 16 phenolic acids and 12 flavonoids were identified. Protocatechuic acid, p-coumaric acid and ferulic acid are the major phenolic acids identified whereas, catechin, apigenin and kaempferol are the major flavonoids identified. In summary, this study proved that coconut testa is a natural source of multiple phenolics acids and flavonoids with potent antioxidant capacity, and it can be used as a natural source of antioxidants.

Assessment and comparison of phytochemical constituents and biological activities of bitter bean (Parkia speciosa Hassk.) collected from different locations in Malaysia

BackgroundParkia speciosa seeds are a common ingredient in Malay cuisine with traditional interest because of its medicinal importance and content of health-promoting phytochemicals. This study evaluated the phytochemical constituents and biological activities (antioxidant and antibacterial activities) of Parkia speciosa Hassk seeds collected from three different regions of Malaysia (Perak, Negeri Sembilan and Johor). Phytochemical constituents (total flavonoid and total phenolic) were measured using the spectrophotometric method, and individual flavonoids and phenolic acids were identified using ultra-high-performance liquid chromatography. Ferric reducing antioxidant potential (FRAP) assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay we used in order to evaluation of antioxidant activities. Disc diffusion method was employed for the evaluation of antibacterial activity of extracts against Gram-positive and Gram-negative bacterial strains.ResultsThe primary screening of phytochemicals showed that P. speciosa seeds contain alkaloids, terpenoids, flavonoids, and phenolics. Samples collected from Perak contained the highest levels of the phytochemical constituents, with highest DPPH and FRAP activity followed by Negeri sembilan and Johor. From the identified compounds, quercetin and gallic acid were identified as the most abundant compounds. Seeds collected from the Perak location exhibited potent antibacterial activity, against both Gram-positive and Gram-negative bacteria strains. Staphylococcus aureus and Bacillus subtilis were recorded as the bacterial strains most sensitive to P. speciosa seed extracts. Correlation analysis showed that flavonoid compounds are responsible for the antioxidant activities of the P. speciosa seeds studied, while antibacterial activity showed a high correlation with the levels of gallic acid.ConclusionsParkia speciosa seed grown in Perak exhibit the highest concentrations of phytochemicals, as well as the highest biological activity. It may also be recommended for the food industry to use seeds from this area for their products, which are going to compete in the expanding functional food markets.

Cultivar affects the phenolic composition and antioxidant properties of commercially available lemon balm (Melissa officinalis L.) varieties

Although agronomic factors affecting essential oil composition within lemon balm (Melissa officinalis L.) are well documented, much less is known about conditions that influence foliar phenolic levels. Therefore in this study, the effect of cultivar and seed company on the phenolic composition and antioxidant properties of five commercially available lemon balm varieties was determined. Cultivar (p = 0.009) and seed company (p = 0.020) had a significant effect on total phenolic concentrations. Analysis of individual phenolic acid levels by high-performance liquid chromatography showed substantial variations in the phenolic acid composition among cultivars. Rosmarinic (p = 0.001), gentisic (p = 0.014), chicoric (p < 0.001), protocatechuic (p = 0.018), and p-coumaric (p < 0.001) acid concentrations were affected by cultivar, although caftaric, caffeic and gallic acids were not. Seed company was a significant factor influencing rosmarinic (p = 0.007), gentisic (p = 0.002), chicoric (p = 0.034) and p-coumaric (p = 0.024) acid content. Cultivar also had a significant influence on FRAP (ferric reducing antioxidant power, p = 0.028) and DPPH (2,2-diphenyl-1-picrylhydrazyl, p = 0.002) antioxidant capacities. These results suggest that both the selection of cultivar and seed origin are important factors influencing the concentration of phenolic compounds and the resulting antioxidant properties within lemon balm.

Effect of cultivars and milling degrees on free and bound phenolic profiles and antioxidant activity of black rice

Six black rice cultivars (Heukjinju, Sintoheugmi, Heukhyangchal 1, Bosukheukchal, Sinnongheukchal, and Josengheukchal) and varying milling degrees (step 0, 0%; step 1, 4.2%; and step 2, 10.5%, w/w) were used to evaluate the effects of cultivars and milling degrees of black rice (Oryza sativa L.) on the total phenolic contents (TPC), total flavonoid contents (TFC), antioxidant activity (2,2-diphenyl-1-picrylhydrazyl free radical assay), and phenolic composition in free and bound phenolic fractions. Unpolished (step 0) Sintoheugmi showed significantly higher TPC, TFC, antioxidant activity, phenolic acid levels, and anthocyanin levels than other unpolished cultivars (p < 0.05). As milling degree increased, TPC, TFC, antioxidant activity, phenolic acid levels, and anthocyanin levels decreased significantly (p < 0.05). TPC, TFC, and antioxidant activity were significantly higher in free phenolic fractions than bound phenolic fractions of black rice extracts, regardless of cultivars (p < 0.05). The major phenolic acid was ferulic acid, and the major anthocyanin found in free phenolic fractions in black rice samples was cyanidin-3-O-glucoside. The sum of individual phenolic acid levels (255.2 ± 0.0 μg/g) and the sum of anthocyanins levels (831.4 ± 0.3 μg/g) were significantly higher in Sintoheugmi black rice than in the other cultivars for step 0 (unpolished rice) (p < 0.05). For step 1 and step 2, Heukjinju black rice contained significantly higher sum of phenolic acid levels and sum of anthocyanin levels than the other cultivars (p < 0.05). For use as a better functional ingredient, it is, therefore, important to consider different milling degrees together with different black rice cultivars having the highest antioxidant component.

Effect of soil phenolic acids on soil microbe of coal-mining depressed land after afforestation restoration by different tree species

Phenolic acids are one of the most important factors that influence microbial community structure. Investigating the dynamic changes of phenolic acids and their relationship with the microbial community structure in plantation soils with different tree species could contribute to better understanding and revealing the mechanisms of microbial community changes under afforestation restoration in coal-mining subsidence areas. In this study, plantations of three conifer and one deciduous species (Pinus koraiensis, Larix gmelinii, Pinus sylvestris var. mongolica, and Populus ussuriensis) were established on abandoned coal-mining subsidence areas in Baoshan District, Shuangyashan City. The contents of soil phenols, 11 types of phenolic acids, and microbial communities in all plots were determined. The results showed that the contents of soil complex phenol in plantations were significantly higher than that of abandoned land overall. Specifically, soils in larch and poplar plantations had higher contents of complex phenol, while soils in larch and Korean pine plantations had greater contents of total phenol. Moreover, soil in the P. koraiensis plantation had a higher content of water-soluble phenol compared with abandoned lands. The determination of 11 phenolic acids indicated that the contents of ferulic acid, abietic acid, β-sitosterol, oleanolic acid, shikimic acid, linoleic acid, and stearic acid were higher in plantation soils. Although soil phenol contents were not related with soil microbial biomass, the individual phenolic acids showed a significant relationship with soil microbes. Ferulic acid, abietic acid, and β-sitosterol showed significant promoting effects on soil microbial biomass, and they showed positive correlations with fungi and fungi/bacteria ratio. These three phenolic acids had higher contents in the poplar plantation, suggesting that poplar affo-restation had a beneficial effect on soil quality in coal-mining subsidence areas.