Abstract
In the current study, changes in secondary metabolite synthesis and the pharmaceutical quality of sabah snake grass leaves and buds were considered in relation to plant age (1 month, 6 months, and 1 year old). The activity of the enzyme chalcone synthase (CHS, EC 2.3.1.74) was measured, as it is a key enzyme for flavonoid production. Significant differences in total flavonoid (TF) production were observed between the three plant growth periods and the different plant parts. The highest contents of TF (6.32 mg/g dry weight [DW]) and total phenolic (TP) (18.21 mg/g DW) were recorded in 6-month-old buds. Among the flavonoids isolated in this study the most important ones based on concentration were from high to low as follows: catechin > quercetin > kaempferol > luteolin. Production of phenolic acids increased from 1 to 6 months, but after 6 months up to 1 year of age, they decreased significantly. The highest contents of caffeic acid (0.307 mg/g DW) and gallic acid (5.96 mg/g DW) were recorded in 1-year and 6-month-old buds, respectively. The lowest and highest activity of CHS was recorded in 1-month and 6-month-old buds with values of 3.6 and 9.5 nkat/mg protein, respectively. These results indicate that the increment in flavonoids and phenolic acids in 6-month-old buds can be attributed to an increase in CHS activity. The highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) activity was observed in the extract of 1-year-old buds followed by 6-month-old buds, with 50% of free radical scavenging (IC50) values of 64.6 and 73.5 µg/mL, respectively. Interestingly, a ferric reducing antioxidant power (FRAP) assay showed a higher activity in 6-month-old buds (488 μM of Fe(II)/g) than in 1-year-old buds (453 μM of Fe(II)/g), in contrast to the DPPH result. Significant correlations (p < 0.05) were observed between CHS enzyme activity and FRAP activity, TF, catechin, and kaempferol content. Extracts of 6-month-old bud exhibited a significant in vitro anticancer activity against HeLa cancer cells with IC50 value of 56.8 µg/mL. These results indicate that early harvesting of snake grass (6-month-old) may yield increased concentrations of secondary metabolites, which are potent antioxidant compounds.
Highlights
As a fine source of bioactive compounds, medicinal plants have long been utilized both in traditional and modern medicine as nutraceuticals as well as food supplements
Catechin was identified in sabah snake grass, with its highest concentration found in 1-year-old plants
The amount of catechin was higher (2.023 mg/g DW) in buds compared to the leaves (1.191 mg/g DW) in 1-year-old plants; in 1- and 6-month-old plants the concentration of catechin was higher in the leaves compared to the buds
Summary
As a fine source of bioactive compounds, medicinal plants have long been utilized both in traditional and modern medicine as nutraceuticals as well as food supplements. Some of the phytochemicals that are extracted from plant sources include phenolics, flavonoids, alkaloids, saponins, tannins, and lignin Such materials are recognized as having the capability to prevent, as well as treat, various health problems such as cancer, heart disease, diabetes, and high blood pressure [2]. Particular factors can affect the flavonoid content in the herbs and medicinal plants These factors include the environmental conditions, year and season, along with the plant’s age, leaf maturity, and similar growth factors. To the best of our knowledge, no other studies have been undertaken to determine the alteration of bioactive compound synthesis and pharmaceutical quality of sabah snake grass at different plant growth periods. Current research is aimed at assessing changes in flavonoid and phenolic acid production in relation to chalcone synthase enzyme activity as well as examining their antioxidant and anticancer activities as a function of the growth period of sabah snake grass
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