Different Concentrations Of Aqueous Extracts Research Articles

Effect ofHibiscus sabdariffaand its Anthocyanins on Some Reproductive Aspects in Rats

An aqueous extract of Hibiscus sabdariffa L. is a common beverage in many parts of the world. Reports on its effect on reproduction are conflicting, with anecdotal evidence that the plant is an aphrodisiac, while others report that it is estrogenic, and adversely affects spermatogenesis in rats. We have studied the effect of different concentrations of aqueous extracts of H. sabdariffa calyces (10%, 15% and 20%) used as drinking water for 10 consecutive weeks, and its anthocyanins (50, 100, 200 mg/kg for 5 days, orally) on the weight and histology of the testis, and on some biochemical constituents in testicular homogenates, in addition to the plasma concentrations of testosterone, luteinizing hormone and estradiol. The possible presence of an estrogenic effect of the extract and anthocyanins on the uteri of immature female rats was also tested. Neither the H. sabdariffa extract nor the anthocyanins significantly altered either testicular weight and histology, or uterus weight. Plasma concentrations of the three hormones studied, the testicular concentrations of protein, reduced glutathione and total cholesterol, and superoxide dismutase activity were all insignificantly affected by either the extract or the anthocyanins, except for a slight, but statistically significant, decrease in testicular protein concentration caused by the 15% aqueous extract when compared with controls. These results suggest that H. sabdariffa exerts no adverse effect on the male reproductive system. Consumption of H. sabdariffa aqueous extract inhibited the growth of the rats compared with the controls.

Cytotoxic effect of Mentha spicata aqueous extract on cancerous cell lines in vitro

Mentha spicata is a herb with several biological properties. Cytotoxicity of essential oils of M. spicata on some cancer cells has been reported. In this study the cytotoxicity of aqueous extract of M. spicata on two tumor cell lines (Wehi-164 fibrosarcoma and U937 leukemic monocyte) has been evaluated in vitro . Wehi-164 and U937 cells were separately cultured in RPMI with 10% FBS. Then the cells at logarithmic growth phase were incubated in the presence of different concentrations of aqueous extract of M. spicata (0.1 to 10 mg/ml) at 24, 48 and 72 h periods. The cell proliferation was assessed with trypan blue dye exclusion and MTT assays. Aqueous extract of M. spicata significantly reduced the proliferation of Wehi-164 and U937 cells dose and time- dependently. The LD 50 values of M. spicata extract were 5.97, 4.63 and 4.77 mg/ml for the Wehi-164 cells and 5.6, 5.3 and 4.84 mg/ml for the U937 cells, after 24, 48 and 72 h treatment respectively. Aqueous extract of M. spicata showed cytotoxic effect in mouse fibrosarcoma Wehi-164 and human monocytic U937 cells. Thus, M. spicata could have potential anti-tumor activity. In vivo studies as well as identification of effective components of M. spicata with anti-cancer activity and their exact mechanism of action could be useful in designing new anti-cancer therapeutic agents.

Efficacy of Limonia acidissima L. (Rutaceae) leaf extract on larval immatures of Culex quinquefasciatus Say 1823

Objective To investigate the role of leaf extract of Limonia acidissima L. (Rutaceae) as a biocontrol agent against the larval form of Culex quinquefasciatus, and characterization of bioactive component responsible for larvicidal activity. Methods Larval mortality of mosquito species was observed after 24, 48 and 72 hours of exposure to different concentrations of aqueous extract, solvent extract and subsequently bioactive compound. The bioactive compound was subjected to IR and GC-MS analysis. Results Mortality rate at 3% concentration of crude extract were highest (90%) amongst all concentrations tested and subsequently highest (95%) mortality was achieved in chloroform: methanol extract at 100 ppm concentrations. IR and GC-MS analysis of bioactive compound revealed the presence of steroid compound which may act as larvicide. Conclusions The chloroform: methanol extract of mature leaves of Limonia acidissima was found to exhibit considerable mosquito larvicidal activity against Culex quinquefasciatus.

Aqueous extract of Ocimum gratissimum Linn and ascorbic acid ameliorate nicotine–induced cellular damage in murine peritoneal macrophage

Objective To test the in vitro protective role of aqueous extract of Ocimum gratissimum Linn. ( O. gratissimum) and ascorbic acid against nicotine-induced murine peritoneal macrophage. Methods Peritoneal macrophages from mice were treated with nicotine (10 mM), nicotine (10 mM) with aqueous extract of O. gratissimum (1 to 25 μg/mL), and nicotine (10 mM) with ascorbic acid (0.01 mM) for 12 h in cell culture media, while the control group was treated with culture media. Levels of free radical generation, lipid peroxidation, protein carbonyls, oxidized glutathione levels and DNA damage were observed and compared. Results Phytochemical analysis of aqueous extract has shown high amount of phenolics and flavonoids compound present in it. The significantly increased free radical generation, lipid peroxidation, protein carbonyls, oxidized glutathione levels and DNA damage were observed in nicotine-treated group as compared to the control group; those were significantly reduced in aqueous extract of O. gratissimum and ascorbic acid supplemented groups. Moreover, significantly reduced antioxidant status in nicotine exposed murine peritoneal macrophage was effectively ameliorated by these two products. Among the different concentration of aqueous extract of O. gratissimum, the maximum protective effect was observed at 10 μg/mL which does not produce any significant change in the normal cell. Conclusions These findings suggest the potential use and beneficial role of O. gratissimum as a modulator of nicotine-induced cellular damage in murine peritoneal macrophage.

Seed treatment with aqueous extract of Viscum album induces resistance to pearl millet downy mildew pathogen

Downy mildew (Sclerospora graminicola [Sacc.] Schroet.) is a serious agricultural problem for pearl millet (Pennisetum glaucum [L.] R. Br.) grain production under field conditions. Six medicinally important plant species Azadirachta indica, Argemone mexicana, Commiphora caudata, Mentha piperita, Emblica officinalis and Viscum album were evaluated for their efficacy against pearl millet downy mildew. Seeds of pearl millet were treated with different concentrations of aqueous extract of the plants to examine their efficacy in controlling downy mildew. Among the plant extracts tested, V. album treatment was found to be more effective in enhancing seed quality parameters and also in inducing resistance against downy mildew disease. Germination and seedling vigor was improved in seeds treated with V. album extracts over control. Seeds treated with 10% concentration of V. album showed maximum protection against downy mildew disease under greenhouse and field conditions. The downy mildew disease protection varied from 44–70% with different concentrations. Leaf extract of V. album did not inhibit sporulation and zoospore release from sporangia of Sclerospora graminicola, indicating that the disease-controlling effect was attributed to induced resistance. Seed treatment with V. album extract increased pearl millet grain yield considerably. In V. album, treated pearl millet seedlings increased activities of peroxidase, and phenylalanine ammonia-lyase enzyme was detected. FTIR analysis of V. album extracts showed the presence of amides and other aromatic compounds which are antimicrobial compounds involved in plant defense.

A Search for Hepatoprotective Activity of Fruit Extract of Mangifera indica L. Against Oxidative Stress Cytotoxicity

Mango (Mangifera indica L.) and their components are commonly used in folk medicine for many curative effects. The protective effects of different concentrations of aqueous extract of Mangifera indica L. fruit (Mango Extract) (20, 50 and 100 microg/ml) and also gallic acid (100 microM) as a pure compound in the extract were examined against oxidative stress toxicity induced by cumene hydroperoxide (CHP) in isolated rat hepatocytes. The extracts and gallic acid (100 microM) protected the hepatocyte against all oxidative stress markers including cell lysis, ROS generation, lipid peroxidation, glutathione depletion, mitochondrial membrane potential decrease, lysosomal membrane oxidative damage and cellular proteolysis. Mango Extracts (20, 50 and 100 microg/ml) were more effective than gallic acid (100 microM) in protecting hepatocytes against CHP induced lipid peroxidation. On the other hand gallic acid (100 microM) acted more effective than Mango Extracts (20, 50 and 100 microg/ml) at preventing lysosomal membrane damage. In addition H(2)O(2) scavenging effect of all extracts were determined in hepatocytes and compared with gallic acid (100 microM). There were no significance differences (P<0.05) between all plant extracts and gallic acid (100 microM) in H(2)O(2) scavenging activity. These results suggest a hepatoprotective role for Mango Extract against liver injury associated with oxidative stress.

A search for hepatoprotective activity of aqueous extract of Rhus coriaria L. against oxidative stress cytotoxicity

The protective effects of different concentrations of aqueous extract of Rhus coriaria L. fruit (75 and 100μg/ml) and also gallic acid (100μM) as one of its main components were examined against oxidative stress toxicity induced by cumene hydroperoxide (CHP) in isolated rat hepatocytes. Both extract concentrations and gallic acid (100μM) significantly (P<0.05) protected the hepatocyte against all oxidative stress markers including cell lysis, ROS generation, lipid peroxidation, glutathione depletion, mitochondrial membrane potential decrease, lysosomal membrane oxidative damage and cellular proteolysis. Aqueous extracts of Rhus coriaria L. (75 and 100μg/ml) were more effective than gallic acid (100μM) in protecting hepatocytes against CHP induced lipid peroxidation (P<0.05). On the other hand gallic acid (100μM) acted more effective than aqueous extracts of Rhus coriaria L. (75 and 100μg/ml) at preventing hepatocyte membrane lysis (P<0.05). In addition H2O2 scavenging effect of both extract concentrations (75 and 100μg/ml) were determined in hepatocytes and compared with gallic acid (100μM). Gallic acid (100μM) was more effective than aqueous extracts of Rhus coriaria L. (75 and 100μg/ml) at H2O2 scavenging activity (P<0.05).

Allelopathic effects of Eucalyptus citriodora on amaryllis and associated grassy weed

A Petri dish assay was carried out for screening different concentrations of aqueous extracts of fresh and dry leaves of Eucalyptus citriodora on germination and seedling growth of wild oat weed (Avena fatua). Seed germination, root and shoot length of wild oat exhibited different degrees of inhibition according to the concentration of the aqueous extract. Maximum inhibitions of germination percentage, root and shoot length were recorded when using 25% fresh leaf extract. Based on this preliminary work (Petri dish assay), studies were conducted under greenhouse conditions at the National Research Center, Egypt, in the two winter seasons of 2006/2007 and 2007/2008 to evaluate the effects of foliar and soil treatments of aqueous extracts of Eucalyptus citriodora fresh and dry leaves on wild oat weed as well as on the growth and flowering of amaryllis (Hippeastrum hybridum), compared with the recommended dose of the herbicide tralkoxydim. Amaryllis fresh and dry weights as well as flowering increased significantly when treated with the previous extracts, especially the fresh leaf extract. However, the fresh and dry weights of wild oat were significantly reduced by the aqueous extracts, either fresh or dry, indicating phytotoxic effects. Tralkoxydim caused complete inhibition of wild oat as compared with the control. The studies involved estimation of the endogenous contents of total phenols in weed. With all the treatments, the inhibitory effects on weeds were correlated with accumulation of the internal contents of total phenols, compared to their respective controls. The amount of phenols correlated well with the weed's growth performance. This study establishes the effect of the aqueous extracts on the weed wild oat, associated with amaryllis, which may serve as a tool in establishing their herbicidal potential.

Efeito de extrato aquoso de Melia azedarach no desenvolvimento das fases imatura e reprodutiva de Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)

The effect of different concentrations of aqueous extracts of Melia azedarach on Spodoptera frugiperda biology was investigated under laboratory conditions. Corn leaves were immersed in solutions with extract concentrations of 0.1%; 1.0% and 5.0% and offered to newly-born larvae. At higher doses (1.0% and 5.0%) the extracts caused 100 % mortality of larvae. Observations of dead larvae showed abnormal moults and death at ecdysis. At the concentration of 0.1%, chinaberry extract increased the larval phase and reduced significantly the larval and pupal weight. Reproduction parameters, as the number of eggs per female, eggs per oviposition and eggs viability were affected using emerged adults from treated larvae with concentration of 0.1% Melia extract. The fecundity was drastically reduced. Survival and duration of egg stage were not affected by the extracts. No effect was observed in relation to attractiveness of caterpillars at first instar in tests with possibility of choice. The chinaberry aqueous extract showed good potential to be used as a control agent for S. frugiperda .

Formulation of health drinks using natural sweetener, its HPTLC method development and validation

Ashwagandha, Tulsi, Mulethi, Awala, Shatavari, Gokharu, Arjun, Giloy, Safed musli, Kalimirchi, Haldi, Jaiphal was used as an active ingredients and aqueous extract of Stevia rebaudiana as natural sweetener with nutraceutical in health dinks. The product was developed by treating concentrates of each crude drug with purified water. TLC profile, HPTLC method development and validation were carried out using Gallic acid as a standard. A new simple, sensitive, selective, precise and robust HPTLC method for analysis of Gallic acid in health drink was developed. Precoated silica health drink aluminium plate 60F-254 (20 × 10 cm) with 200 µm thickness was used as stationary phase while toluene: ethyl acetate: formic acid: ethanol (6: 4: 0.3: 0.4) system was developed as a mobile phase. Spectrum analysis showed the same Rf values and spectrum pattern of standard and sample. The method was validated by using accuracy, precision, linearity, robustness, ruggedness and recovery as applicable parameters. The developed method was quite good and most sensitive for the present products. The unpleasant and bitter taste of the product was masked by different concentrations of aqueous extract of Stevia. Sweetness potency was determined by taste evaluation method. 1% Stevia extract is sufficient to produce most palatable and acceptable sweet preparation. Key words: Formulation, TLC profile, HPTLC method development, validation, gallic acid, health drinks, Stevia rebaudiana.

Cytotoxic effect of saffron stigma aqueous extract on human transitional cell carcinoma and mouse fibroblast.

Saffron has been suggested to have inhibitory effects on tumoral cells. We evaluated the cytotoxic effect of aqueous extract of saffron on human transitional cell carcinoma (TCC) and mouse non-neoplastic fibroblast cell lines. Human TCC 5637 cell line and mouse fibroblast cell line (L929) were cultivated and incubated with different concentrations of aqueous extract of saffron stigma (50 microg/mL to 4000 microg/mL). Cytotoxic effect of saffron was evaluated by morphologic observation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay after 24, 48, 72, and 120 hours in each cell line. After 24 hours, morphological observations showed growth inhibitory effects at saffron extract concentrations higher than 200 microg/mL for L929 cells and at concentrations of 50 microg/mL to 200 microg/mL for the TCC cells. These changes became more prominent after 48 hours. However, significant growth inhibitory effects of the extract were shown at concentrations of 400 microg/mL and 800 microg/mL. Higher concentrations of saffron correlated inversely with cell population of both cell lines. Significant reduction of the survived cells was seen at concentrations of 400 microg/mL and 2000 microg/mL for TCC and L929 cell lines, respectively. After 120 hours, decrease in the percentage of survived cells at higher concentrations of saffron extract was seen in both cell lines. At a concentration of 800 microg/mL, the survived L929 cells plummeted to less than 60% after 120 hours, while no TCC cells survived at this time. No L929 cells survived at 2000 microg/mL. Saffron aqueous extract has inhibitory effects on the growth of both TCC 5637 and normal L929 cell lines. This effect is dose dependent.

Indução de resistência em plantas de berinjela por Lentinula edodes e Agaricus blazei contra Ralstonia solanacearum: aspectos bioquímicos e biomassa vegetal

A murcha bacteriana, causada por Ralstonia solanacearum, é considerada uma doença de importância para a cultura da berinjela, sendo de difícil controle. O controle de doenças através de indução de resistência é um método que vêm se revelando como promissor. Basidiomas de Agaricus blazei e Lentinula edodes possuem substâncias do tipo antibiótico e outras substâncias capazes de atuarem como elicitoras da resposta de resistência em plantas, mostrando-se assim promissores no controle alternativo de fitopatógenos. O presente trabalho foi conduzido com o objetivo de estudar o efeito de extratos aquosos dos fungos e do indutor químico acibenzolar-S-metil (aSm) sobre o crescimento da bactéria in vitro e o controle da murcha bacteriana, bem como investigar seu efeito sobre a atividade de determinadas enzimas da planta. O efeito inibitório sobre o patógeno foi avaliado usando diferentes concentrações dos extratos aquosos. A indução de resistência foi estudada em plantas tratadas com o indutor biológico e químico, medindo-se a intensidade de murcha e determinando-se as alterações de algumas enzimas. Os resultados revelaram que os isolados de A. blazei e L. edodes, utilizados em diversas diluições, não exerceram efeito inibitório in vitro. Em relação à indução de resistência, extratos dos isolados Abl-11 e Abl-28 de A. blazei (15%, v/v) e o aSm (0,05 g/L) promoveram redução significativa na ocorrência de folhas murchas, quando aplicados dois dias antes da inoculação. O aumento na atividade de peroxidase foi verificado em plantas tratadas com extratos de Abl-11, Abl-28 e com suspensão de aSm. A atividade de quitinase, fenilalanina amônia-liase e polifenoloxidase não foi alterada nas plantas tratadas com extrato de Abl-28 e com o aSm. No entanto, plantas de berinjela tratadas com Abl-11 exibiram uma aumento na atividade de fenilalaniana amônia-liase e de polifenoloxidase, enquanto que a atividade de quitinase não foi alterada. Com base nos resultados, ficou evidenciado que o aSm e os isolados Abl-11 e Abl-28 de A. blazei apresentam potencial para induzir resistência em berinjela contra R. solanacearum.

Inhibition of Streptococcus mutans adhesion to buccal epithelial cells by an aqueous extract of Thymus vulgaris

The aim of this study was to investigate the effect of an extract of Thymus vulgaris (thyme) on the growth of Streptococcus mutans (S. mutans) and the adhesion of this bacterium to human buccal epithelial cells. Different concentrations of an aqueous extract of thyme were prepared and the effects investigated on growth of S. mutans. Furthermore, the effect of these extracts on adhesion of S. mutans to buccal epithelial cells was also investigated and compared with the effects of chlorhexidine digluconate. The data revealed that exposure of S. mutans to thyme extract showed a time and concentration-dependent decrease in bacterial viability. The greatest effect was observed when S. mutans had been exposed to 20% thyme extract for a period of 48 h which resulted in 96% inhibition of bacterial growth. Furthermore, the adhesion of S. mutans to buccal epithelial cells was also reduced when either buccal epithelial cells or S. mutans had been pre-incubated with different concentrations of aqueous thyme extracts (83-98% and 75-89% inhibition respectively). There was also greater reduction in the adherence of bacterial cells to buccal epithelial cells after mouth rinsing with 20% aqueous thyme extract compared to rinsing with chlorhexidine digluconate (45% and 89% inhibition of bacterial adhesion respectively). The diminished adherence of S. mutans to buccal epithelial cells after exposure to various concentrations of aqueous thyme extract as well as the antimicrobial properties of this plant may have clinical relevance.

Inhibitory effects of Albizia lebbeck leaf extracts on germination and growth behavior of some popular agricultural crops

An experiment was conducted to observe the inhibitory effects of the leaf extracts derived from Albizia lebbeck (L.) Benth. on germination and growth behavior of some popular agricultural crops (receptor) of Bangladesh. Experiments were set on sterilized petridishes with a photoperiod of 24 h at room temperature of 27-30℃. The effects of the different concentrations of aqueous extracts were compared to distil water (control.). The aqueous extracts of leaf caused significant inhibitory effect on germination, root and shoot elongation and development of lateral roots of receptor plants. Bioassays indicated that the inhibitory effect was proportional to the concentrations of the extracts and higher concentration (50%-l00%) had the stronger inhibitory effect whereas the lower concentration (l0%-25%) showed stimulatory effect in some cases. The study also revealed that, inhibitory effect was much pronounced in root and lateral root development rather than germination and shoot growth.

In vitro production of Indian citrus ringspot virus (ICRSV) free kinnow plants employing phytotherapy coupled with shoot tip grafting

This paper reports the elimination of Indian citrus ringspot virus (ICRSV) from “kinnow” (Citrus nobilis Lour × Citrus deliciosa Tenora) employing phytotherapy coupled with shoot tip grafting under in vitro conditions. Nodal segments from infected mother plant (indexed by indirect enzyme-linked immunosorbent assay [ELISA] and reverse transcriptase PCR [RT-PCR]) were cultured on Murashige and Skoog medium containing 2iP (1 mg/l or 4.9 μM) and malt extract (800 mg/l) along with different concentrations of aqueous extracts from leaves of Azadirachta indica (Neem), Sorghum vulgare (Jowar), and roots of Boerhaavia diffusa (Punarnava). Shoot tips were excised from the nodal sprouts and grafted on to rough lemon (Citrus jambhiri) under aseptic conditions. Maximum effect (50% virus elimination) was seen for aqueous leaf extracts of A. indica followed by B. diffusa root extract (42.86%) and S. vulgare leaf extract (31.58%). Plants/plantlets were considered virus-free only when showing negative reactions by both indirect ELISA and RT-PCR.

Effect of glutathione on arecanut treated normal human buccal fibroblast culture.

Experimental studies have shown arecanut to be a cytotoxic substance with mutagenic and carcinogenic potential. The present study was undertaken to evaluate the effect of glutathione on arecanut treated human buccal fibroblast culture and its potential as a chemopreventive agent. Fibroblast culture was done in Dulbecco's Modified Eagle's Medium MEM) supplemented with 10% Fetal Calf Serum (FCS) and antibiotic at 370C degrees in an atmosphere of 5% carbon di-oxide and 95% air. The fibroblast cells were subjected to different concentrations of aqueous extracts of raw and boiled arecanut. Fibroblasts were plated in two 24-well culture plates and in each plate, cells were dividt,ednto 2 groups; 600gg microml of reduced glutathione was added to the first group of cells; subsequently, aqueous extracts of raw and boiled arecanut at least and highest concentrations i.e., 20j. microml and 100lg microml were added to the first group of cells in the respective plates whereas the second group served as a control. The morphological alterations and cell survival were assayed at 24, 48, 72, and 96 hours. Results Morphologically, the initial (10 hours) attached fibroblast cells were converted from spheroidal shape towards hexagonal and finally to a fully extended spindle shaped configuration. The three morphological types of fibroblasts at 48 hours were F-I, F-II and F-III. Aqueous extract of raw arecanut exhibited significant cytotoxicity (p < .0 001) at all time periods studied, when compared against the control values of untreated fibroblasts. Addition of reduced glutathione to cultures showed a significant (p < 0. 001) reduction in cytotoxicity, as indicated by higher optical density values and morphological reversion to the spindle-shaped configuration. Co Addition of glutathione reduced the cytotoxic and morphological alterations of the fibroblasts treated with aqueous extracts of both raw and boiled arecanut.

The potential for controlling post‐flowering pests of cowpea,Vigna unguiculataWalp. using neem,Azadirachta indicaA. Juss

Abstract The insecticidal activity of neem, Azadirachta indica A. Juss., was tested on two major cowpea pests using different concentrations of aqueous extracts, and powders of both neem seed and kernel. The pests were larvae of Maruca testulalis Geyer (Lepidoptera: Pyralidae), the legume pod borer and Clavigralla tomentosicollis Stal (Hemiptera: Coreidae), the cowpea coreid bug. Ife Brown, an improved local cowpea variety, and IT84S‐2246, a breeding line from IITA grain legume programme, were used in the study. Neem proved effective in acting as an insecticide and affected the rates of development of both pests at concentration as low as ca. 9% solution (wt/vol.). Imaginal survival was found to decrease with increasing neem concentration, but a point was reached where further increase in the amount of neem produced no significant changes in survival rates. Most bug nymphs died within 9 days of infestation but those which survived to adult in the 5% solution (wt/vol.) of the seed extract took almost twice...

Effect of fly ash extract on growth and development of corn and soybean seedlings

Different concentrations of aqueous extract of fly ash were prepared by soaking air dried fly ash and mixing thoroughly with an electric blender. Extracts were then applied to the seeds of corn (Zea mays L.) and soybean (Glycine max L.) after being filtered through a Whatman No. 42 filter paper. Fly ash extract in the lower concentration range of 0.5 to 1.0% (W/V) had no significant effect on germination and seedling growth of each of the two crops. Higher concentrations of fly ash extracts, however, had deleterious effects on the percentage of germination, viability, number of roots, shoot and root length, fresh weight and dry weight of seedlings of both the crops. The elemental concentrations in shoot and root systems of control seedlings of corn and soybean were found to be the same, whereas in the extract treated corn and soybean seedlings, a relatively high elemental concentration was found in roots as compared to shoots.

Effects of sludge extracts on seed germination and root elongation of crops

Different concentrations of aqueous extracts of activated sludge were prepared by extracting with distilled water in an electric blender. They were then applied to the seeds of flowering Chinese cabbage, Brassica parachinensis and Chinese radish, Raphinus sativus var. longipinnatus, after being filtered through a Whatman No. 42 filter paper. Seed germination and root elongation of the crops were retarded, especially at higher concentrations of sludge extracts (0·8 and 1%). Studies of root elongation clearly showed the effect of retardation, even at a concentration as low as 0·2%, although the percentage of seed germination at this particular concentration was similar to that of the control group which was treated with distilled water only. The seeds of flowering Chinese cabbage were more sensitive to the sludge extracts than the seeds of Chinese radish. The harmful effects of substances other than heavy metals in the aqueous extracts of sewage sludge on seed germination and root elongation were revealed when the seeds of B. parachinensis were treated with mixtures of heavy metals with concentrations equivalent to those obtained in different portions of sludge extracts.

Corrosion inhibition by naturally occurringsubstances—I. The effect of Hibiscus subdariffa (karkade) extract on the dissolution of Al and Zn

The thermometric, the weight-loss and the galvanostatic polarization techniques wereused to establish the inhibition of the dissolution of Al and Zn in HCl and NaOH by different concentrations of aqueous extract of Hibiscus subdariffa (Karkade). The extent of corrosion inhibition as measured by the three techniques is comparable. The results indicated that the additive acts by way of adsorption on both cathodic and anodic corrosion areas. Curves representing the variation of the reaction number (R.N.), in thermometric experiments, and the decrease in weight as a function of the concentration of the additive, are invariably sigmoid in nature. When present in enough amounts, the additive decreases the dissolution rate by as much as 85 per cent of the value recorded in its absence. The two main constituents of the aqueous extracts of Hibiscus subdariffa, namely the organic acids and the colouring materials were separated and tested independently for surface activity. Both constituents were effective in retarding the dissolution of the two metals; but the activity of the colouring portion was considerably higher than that of the organic acids.