Rajani Kurup

Distribution of naphthoquinones, plumbagin, droserone, and 5-O-methyl droserone in chitin-induced and uninduced Nepenthes khasiana: molecular events in prey capture

Prey capture and digestion in Nepenthes spp. through their leaf-evolved biological traps involve a sequence of exciting events. Sugar-rich nectar, aroma chemicals, narcotic alkaloid secretions, slippery wax crystals, and other biochemicals take part in attracting, capturing, and digesting preys in Nepenthes pitchers. Here we report the distribution of three potent naphthoquinones in Nepenthes khasiana and their roles in prey capture. Plumbagin was first detected in N. khasiana, and its content (root: 1.33 ± 0.02%, dry wt.) was the highest found in any natural source. Chitin induction enhanced plumbagin levels in N. khasiana (root: 2.17 ± 0.02%, dry wt.). Potted N. khasiana plants with limited growth of roots and aerial parts, showed higher levels of plumbagin accumulation (root: 1.92 ± 0.02%; root, chitin induction: 3.30 ± 0.21%, dry wt.) compared with field plants. Plumbagin, a known toxin, insect ecdysis inhibitor, and antimicrobial, was also found embedded in the waxy layers at the top prey capture region of N. khasiana pitchers. Chitin induction, mimicking prey capture, produced droserone and 5-O-methyl droserone in N. khasiana pitcher fluid. Both these naphthoquinone derivatives provide antimicrobial protection to the pitcher fluid from visiting preys. A two-way barrier was found between plumbagin and its two derivatives. Plumbagin was never detected in the pitcher fluid whereas both its derivatives were only found in the pitcher fluid on chitin induction or prey capture. The three naphthoquinones, plumbagin, droserone, and 5-O-methyl droserone, act as molecular triggers in prey capture and digestion in the carnivorous plant, N. khasiana.

Levodopa in Mucuna pruriens and its degradation

Mucuna pruriens is the best known natural source of L-dopa, the gold standard for treatment of Parkinsonism. M. pruriens varieties are protein rich supplements, and are used as food and fodder worldwide. Here, we report L-dopa contents in seeds of fifty six accessions of four M. pruriens varieties, M. pruriens var. pruriens, M. pruriens var. hirsuta, M. pruriens var. utilis and M. pruriens var. thekkadiensis, quantified by HPTLC-densitometry. L-dopa contents varied between 0.58 to 6.42 (%, dr. wt.). High and low L-dopa yielding genotypes/chemotypes of M. pruriens could be multiplied for medicinal and nutritional purposes, respectively. HPTLC profiles of M. pruriens seeds on repeated extraction (24 h) in 1:1 formic acid-alcohol followed by development in butanol:acetic acid:water (4:1:1, v/v) showed consistent degradation of L-dopa (Rf 0.34 ± 0.02) into a second peak (Rf 0.41 ± 0.02). An average of 52.11% degradation of L-dopa was found in seeds of M. pruriens varieties. Since M. pruriens seeds and/or L-dopa are used for treatment of Parkinson’s disease and as an aphrodisiac both in modern and/or traditional systems of medicine, the finding of high level of L-dopa degradation (in pure form and in M. pruriens extracts) into damaging quinones and ROS is very significant.

Chemical Composition and Antibacterial Activity of the Rhizome and Leaf Oils of Amomum Hypoleucum Thwaites

Abstract Essential oils from the rhizomes and leaves of Amomum hypoleucum were hydrodistilled and characterized by GC/FID and GC/MS. Nineteen constituents comprising 93.0% were identified from the rhizome oil. Cryptone (15.4%), β-pinene (11.9%) and caryophyllene oxide (7.6%) were the major constituents in the rhizome oil. Fifty-two constituents comprising 97.6% were identified from the leaf oil. (E)-Nerolidol (26.5%), α-fenchyl acetate (15.0%) and β-caryophyllene (8.4%) were the major constituents in the leaf oil. These oils showed good antibacterial activity against the Gram-negative bacteria, Pseudomonas aeruginosa, Salmonella typhi and Escherichia coli.

Chemical Composition of the Leaf Oils of Myristica malabarica Lam. and Gymnacranthera canarica (King) Warb.

Abstract Essential oils from the leaves of Myristica malabarica and Gymnacranthera canarica (Myristicaceae) were isolated by hydrodistillation and analyzed by GC/FID and GC/MS. Seventy-six constituents (98.5%) with β-caryophyllene (27.3%), α-humulene (13.8%) and α-copaene (11.5%) as major components were identifed from the leaf oil of M. malabarica. Also, seventy-six constituents (98.1%) with β-caryophyllene (23.4%), linalool (13.4%) and α-humulene (11.3%) as major constituents were identified from the leaf oil of G. canarica. Sesquiterpene hydrocarbons constituted 77.3% in M. malabarica leaf oil and 58.1% in G. canarica leaf oil.

HPTLC-based quantification of camptothecin in Ophiorrhiza species of the southern Western Ghats in India

Abstract Camptothecin (CPT), a modified monoterpene indole alkaloid, is a potential anticancer drug, and due to high demand, search for its new plant-based sources is a priority. Genus Ophiorrhiza is a candidate group in the search for new resources of CPT. Here, CPT contents in 38 Ophiorrhiza accessions, belonging to 11 species and 3 varieties, collected from the southern Western Ghats region in India were quantified by HPTLC-densitometry. Ophiorrhiza mungos (396.54 μg/g, dr. wt.) and O. mungos var. angustifolia (373.19 μg/g, dr. wt.) were the two best CPT sources among the screened species/varieties. O. rugosa var. decumbens (18.55 μg/g, dr. wt.) and O. hirsutula (17.14 μg/g, dr. wt.) showed moderate contents of CPT. This is the first systematic CPT screening of O. hirsutula, O. barnesii, O. incarnata, O. radicans and O. villosa. This study shows the significance of choosing high CPT-yielding ecotypes/chemotypes of Ophiorrhiza species or varieties for commercial purposes.

Chemical Composition of Rhizome Essential Oils of Amomum agastyamalayanum and Amomum newmanii from South India

Abstract Chemical composition of rhizome essential oils of Amomum agastyamalayanum and A. newmanii from south India were analyzed by gas chromatographic techniques. Major constituents in A. agastyamalayanum rhizome oil were allo-aromadendrene (16.2 %), β-pinene (8.7 %) and (E)-caryophyllene (8.5 %). Santolina triene (42.2 %) and α-pinene (17.1 %) were the major constituents in A. newmanii rhizome oil. Monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes and other constituents in A. agastyamalayanum/A. newmanii rhizome oils were 16.3 %/73.7 %, 10.4 %/ 6.9 %, 48.8 %/13.1 %, 19.4 %/3.4 % and 2.1 %/1.0 %, respectively. This is the first chemical profiling study of these two endemic Amomum species.