Advances in cyanogenic glycosides biosynthesis and analyses in plants : a review

A number of species of plants produce repertoire of cyanogenic glycosides via a common biosynthetic scheme. Cyanogenic glycosides play pivotal roles in organization of chemical defense system in plants and in plant–insect interactions. Several commercial crop plants such as sorghum (Sorghum bicolor), cassava (Manihot esculenta) and barley (Hordium vulgare) are cyanogenic and accumulate significant amounts of cyanogenic glycosides. The study of biosynthesis of dhurrin in sorghum has underpinned several early breakthroughs in cyanogenic glycoside researches. Despite great deal of structural diversity in cyanogenic glycosides, almost all of them are believed to be derived from only six different amino acids L-valine, L-isoleucine, L-leucine, L-phenylalanine, or L-tyrosine and cyclopentenyl-glycine (a non protein amino acid). Our knowledge about biosynthesis of cyanogenic glycosides and molecular regulatory processes underlying their biosynthesis has been increased impressively in the past few years. The rapid identification, characterization and cloning of genes encoding enzymes of the cyanogenic glycoside biosynthetic and catabolic pathways from several plants has greatly facilitated our understanding of cyanogenic glycosides biosynthesis and regulation. Today it is known that enzymes of cyanogenic glycoside biosynthetic pathway in sorghum are organized as metabolon most likely to those of other secondary metabolic pathways. Knowledge of state of art of biosynthesis and regulation of cyanogenic glycosides made possible the metabolic engineering of these pathways resulting in development of transgenics of cassava, tobacco, lotus and Arabidopsis with manipulated cyanogenic glycosides content. Simultaneously, many new developments have been witnessed in methods/techniques/ procedures for detection of cyanogenic glycosides in plant samples, foods and foodstuffs. The present review sequentially discusses all of these issues with updated information gathered from the published reports on cyanogenic glycosides

Effects of sodium nitroprusside activity of acid and alkaline invertases and alkaline phosphatase in lemongrass (Cymbopogon flexuosus Steud) Wats

Here we report the effects of SNP, a nitric oxide donor on sucrose metabolizing enzymes, acid and alkaline invertase (EC 3.2.1.26 and 3.2.1.153) and ubiquitous alkaline phosphatase (EC 3.1.3.1) in four lemongrass varieties viz., Krishna, Cauveri, Nima and Cheerharit. For the study, two 15 d lemongrass tillers were cut and immediately dipped into the test tubes containing SNP solution (5 mL) of variable strength (1 to 5 mM) and one without SNP (as control); kept for 4 h under mild sunlight. The results revealed that moderate SNP concentration (2 mM) was most effective, caused drastic reduction (40%) in protein content in var. Nima followed by Krishna (33%), Cauveri (17%) and Cheerharit (12%). In contrast, SNP (1 mM) has impressively enhanced protein content in all the lemongrass varieties. The SNP (2 mM) markedly inhibited the activity of acid invertase by 38% in Cheerharit, 35% Nima and 28% Cauveri whereas and alkaline invertase by 21, 28 and 24% respectively in var. Cheerharit, Nima and Krishna. Similarly, SNP (5 mM) severely inhibited (~ 63%) the activity of the ALP in lemongrass var. Cauveri and Nima, 50% in Krishna and relatively less 23% in Cheerharit as compared to the control. However, in var. Nima, 50% loss in ALP activity had already been occurred after 2 mM SNP treatment. These results primarily suggests that NO interferes sucrose metabolism by anonymously hindering the activity of acid and alkaline invertase and ubiquitous alkaline phosphatase in lemongrasses

Antimicrobial activity of Acorus calamus (L.) rhizome and leaf extract

Antimicrobial activity of Acorus calamus rhizome and leaf extracts obtained with different solvents viz., petroleum ether, chloroform, hexane and ethyl acetate was evaluated. Extracts obtained with ethyl acetate among others were found to be highly effective. Rhizomes and leaf ethyl acetate extracts exhibited pronounced antifungal activity with diameter zone of inhibition ranged from 20-28 and 18-25 mm as well as antiyeast activity with diameter zone of inhibition ranged from 22-25 and 20-23 mm, respectively. The minimum inhibitory concentration (MIC) of the rhizome and leaf extracts for antifungal activity measured was 2-4mg/ml, except Penicillium chrysogenum whereas against yeasts was relatively higher, 4-5 and 6-8 mg/ml. MIC value for antibacterial activity was comparatively very high ~16-42 mg/ml. In addition, authentic α- and β-asarones were also tested for their antimicrobial potential. Both α- and β-asarones exhibited very strong antimicrobial activities against the fungi and yeasts than those of rhizome and leaf extracts. The study clearly suggested that A. calamus rhizomes and leaves must possess active principle α- and β-asarones which is believed to be responsible for their antimicrobial activities. Both rhizomes and leaf extracts, however, had no antibacterial activity except E. coli

A study on development changes in essential oil content and composition in Cymbopogon flexuosus cultivar Suvarna

Cymbopogon flexuosus (Steud.) cv. Suvarna produces an essential oil with unique lemon like aroma which is broadly used in flavors, fragrance, perfumery and pharmaceuticals. Here we report changes in essential oil content and compositions during C. flexuosus cv. Suvarna leaf development, leaf positions and leaf age. Essential oils were isolated by hydro-distillation of leaves harvested at six different developmental stages (10-50 days), 1st-5th leaf positions and three parts (basal, middle and apical) of the leaves. Analyses of essential oils by gas chromatography and GC-MS have identified 20 different terpenoids constituents with citral as the major monoterpene. The study showed that essential oil content was highest in early stages (10-20 days) of leaf development, then declined substantially. Similar pattern of essential oil content was observed between the 1st-5th leaf positions and the basal-apical parts within a leaf. Essential oil compositions were also markedly fluctuated. Percentage together of geranyl acetate and geraniol declined rapidly from 32% to 4% on 10th and 20th days, respectively; while percentage of citral (geranial + neral) increased correspondingly from 56% to 81% on 10th and 20th days, respectively. Similar changes in monoterpene composition were observed in leaf positions and leaf age (basal to apical part). Thus the study revealed that accumulation of essential oil depends on the developmental stages of the concerned plant parts and changes in essential oil content is also reflected by compositional changes in oil constituents

Geranyl acetate esterase (GAE) inhibitory activity of Neolamarckia cadamba fruit extract

Neolamarckia cadamba commonly known as the kadamb tree-is well known in Ayurveda and other traditional literature in India for it’s plenty of medicinal properties. Here we report the unique property of the methanol extract of its fruit and a compound isolated from it to inhibit the geranyl acetate esterase (GAE) of lemongrass. The GAE inhibitory activities of the methanol extract and the compound were determined by three procedures, spectrophotometric para-nitrophenyl acetate (p-NPA) assay, polyacrylamide gel electrophoresis (PAGE) and gas chromatography (GC). The results of p-NPA assay revealed that the fruit extract and its compound (10 mg/ml) caused significant inhibition (45%) of GAE activity as compared to the control. PAGE analysis revealed complete inhibition of one of the major isoenzyme of GAE (isoenzyme-II) by both the fruit extract and its isolated constituent. Gas chromatographic analysis showed the fruit extract and its compound caused drastic inhibition of GAE isoenzyme-II by 36 and 46%, respectively. The presence of –C=O and –OH groups in the compound as revealed by FTIR analysis indicated that it belongs to flavonoids. To the best of our knowledge this is the first report on GAE inhibitory activity of N. cadamba fruit methanol extract and its isolated constituent which could be implicated in the future to decipher the catalytic mechanism of GAE. The purification and detailed characterization of the isolated compound is in progress

Sodium nitroprusside affects the level of anthocyanin and flavonol glycosides in pea (Pisum sativum L. cv. Arkel) leaves

The effects of sodium nitroprusside (SNP), a nitric oxide (NO) donor were investigated on the levels of anthocyanin and flavonol glycoside in pea (Pisum sativum L.) cv. Arkel leaves. The study was conducted in leaf discs (ca. 20 mm2) prepared from the youngest leaves. The anthocyanin and flavonol glycosides content diminish significantly (~ 21% of each) in leaf discs following 1 mM SNP (1 mM) treatment for 3 h under light (600 μmol M-2.s-1). However, a huge increase both in the levels of anthocyanin and flavonol glycosides, 72 and 53% respectively was recorded after 2 h of 1 mM SNP treatment. 0.5 mM SNP treatment of the leaf discs did not change the anthocyanin level but considerable declined (~13%) was observed in the level of flavonol glycosides as compared to the control. Surprisingly, the anthocyanin content in no SNP treated leaf discs after 3 h of incubation under light (600 μmol M-2.s-1) increased rapidly by 72% while flavonol glycosides content by 15% only. The photosynthetic capacities of SNP treated leaf discs were drastically inhibited. The study prelude that NO in combination of light influence the accumulation of anthocyanin and flavonol glycosides in pea leaves

Sodium silicate mediated response of antioxidative defense system in Lycopersicon esculentum mill. under water stress

The present study was designed to study the effect of water stress on Lycopersicon esculentum Mill. and role of sodium silicate in the protection of tomato plants under water deficit condition.Different biochemical parameters such as photosynthetic pigments, protein, sugar, MDA content, proline, nitrate reductase activity and activities of antioxidant enzymes (SOD, CAT, APX and POX) were examined in tomato leaves at 40 and 60 DAS by the standard methods. The lycopene and β-carotene contentsin tomato fruits were also analyzed at 60, 65 and 70 DAS.Water stress significantly decreased relative water content (RWC), pigment content, sugar and protein contents in tomato leaves at 60 DAS but the accumulation of proline was stimulated in tomato leaves under water deficit condition. The activities of antioxidant enzymes such as SOD, CAT, APX and POX were significantly increased under (3d and 6d) water stress condition at 60 DAS.This study offers first hand information on the water stress-induced oxidative stress in Lycopersicon esculentumand development of antioxidative defense system against drought.The results obtained clearly indicated the positive impact of sodium silicate in protection of tomato plants under water deficit condition

Purification and characterization of a 1-deoxy-D-xylulose 5-phosphate synthase from Cymbopogon flexuosus

Here we report purification and characterization of the enzyme 1-deoxy-D-xylulose 5-phosphate synthase (DXS) of the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway from lemongrass (Cymbopogon flexuosus) leaves. The DXS catalyzes the condensation of pyruvate and glyceraldehyde 3-phosphate (G3P) to produce 1-deoxy-D-xylulose 5-phosphate (DOXP), which is the first and rate-limiting step of the MEP pathway. It is the main flux-controlling step and an attractive target to manipulate the formation of the MEP-derived products. The DXS was extracted from immature (15 days old) leaves of lemongrass cv. Suvarna and purified to homogenity using ion exchange DEAE column and gel filtration (Sephadex G-150) chromatography. The purified DXS was referred as CfDXS. The CfDXS had specific activity 8.56 U/mg. The Km values for the two substrates, pyruvate and G3P were 4.4 and 8.8 μM, respectively and for the cofactor TPP 62 μM. The Vmax of the CfDXS was 20 μmol/min. The optimum pH and temperature of the CfDXS were 7.5 and 40 °C, respectively. The CfDXS activity enhanced significantly in the presence of Mg2+ (1 mM), whereas affected moderately by Mn2+ and Zn2+ (1 mM each). The enzyme was purified upto 11.64 fold with an yield of 32.34%. Its molecular weight was 130 kDa. The DXS was quite stable and retaining more than 80% of the initial activity upon storage at 4 °C in 100 mM Tris-HCl buffer (pH 8) for one month

A Study on Antimicrobial Activities of Essential Oils of Different Cultivars of Lemongrass (Cymbopogon flexuosus)

Background: Cymbopogon flexuosus popularly known as lemongrass provides a lemon scented essential oil which is widely used in flavour and fragrance, perfumery, food and pharmaceuticals. The aim of the present study was to assess antimicrobial activities of essential oils of three lemongrass cultivars viz., Pragati, Praman and Suvarna. Methods: Essential oils were isolated from one month old plants by hydro-distillation in mini Clevenger apparatus for 2 h. Antimicrobial activities were determined by agar well diffusion method Results: Lemongrass oils exhibited strong antimicrobial activity against all the microbes except E coli. Mean inhibition zone diameter (mm) against bacteria was ranged 27-38 mm. B. Subtilis was the most sensitive bacterium to all essential oils. Essential oils also showed strong antifungal effects against both A. niger and C. albicans with mean inhibition zone diameter (mm) values 20-26 and 27-29 mm, respectively. Statistical analyses revealed that antimicrobial activity shown by essential oils were significant (p > 0.05). Conclusion: The study revealed strong antimicrobial potential of the essential oil against pathogenic microbial strains which may be of high clinical importance in future