Natural Science Foundation of China[30000213, 30370160, 30670214]; National Basic Research Program of China (973 Program)[2009CB522300]; Chinese Academy of Sciences

Meliaceous limonoids: chemistry and biological activities.

Phytoremediation is a holistic approach and can be used in large scale to remediate the contaminated land resources. Although the concept of phytoremediation is few decades old and has been applied on a wide range of pollutants, but their sustainability is still questioned at various scientific forums. Therefore, it is the need of the hour to remediate our valuable resources with due considerations for future generations. Such a synergistic bonding by using potential energy crops in phytoremediation programs would be useful to generate new bioenergy resources along with the remediation of contaminated soil. There are several energy crops in the world, but four promising and dedicated energy crops i.e. Miscanthus, Ricinus, Jatropha, Populus have primarily considered in this review to accomplish energy demands with their phytoremediation potential. These four energy crops also act as potential carbon sink and offer an additional profit as carbon tax credits. In recent time we have been able to improve our understanding in phytoremediation, but use of energy plants were not considered so far to make this venture socio-economically acceptable to the society. The present review provides a strategy for linking energy crops in phytoremediation to resolve the sustainability issues and effectively solve the challenges of ever increasing contaminated sites and biofuel demands now and for future.

Energy crops in sustainable phytoremediation

Plants produce an array of specialized metabolites, including chemicals that are important as medicines, flavors, fragrances, pigments and insecticides. The vast majority of this metabolic diversity is untapped. Here we take a systematic approach toward dissecting genetic components of plant specialized metabolism. Focusing on the terpenes, the largest class of plant natural products, we investigate the basis of terpene diversity through analysis of multiple sequenced plant genomes. The primary drivers of terpene diversification are terpenoid synthase (TS) “signature” enzymes (which generate scaffold diversity), and cytochromes P450 (CYPs), which modify and further diversify these scaffolds, so paving the way for further downstream modifications. Our systematic search of sequenced plant genomes for all TS and CYP genes reveals that distinct TS/CYP gene pairs are found together far more commonly than would be expected by chance, and that certain TS/CYP pairings predominate, providing signals for key events that are likely to have shaped terpene diversity. We recover TS/CYP gene pairs for previously characterized terpene metabolic gene clusters and demonstrate new functional pairing of TSs and CYPs within previously uncharacterized clusters. Unexpectedly, we find evidence for different mechanisms of pathway assembly in eudicots and monocots; in the former, microsyntenic blocks of TS/CYP gene pairs duplicate and provide templates for the evolution of new pathways, whereas in the latter, new pathways arise by mixing and matching of individual TS and CYP genes through dynamic genome rearrangements. This is, to our knowledge, the first documented observation of the unique pattern of TS and CYP assembly in eudicots and monocots.

Investigation of terpene diversification across multiple sequenced plant genomes

This review described the physiological and biochemical effects of various secondary metabolites from Meliaceae against major Lepidopteran insect pest including, Noctuidae and Pyralidae. The biochemical effect of major Meliaceae secondary metabolites were discussed more in this review. Several enzymes based on food materials have critical roles in nutritional indices (food utilization) of the insect pest population. Several research work has been referred and the effect of Meliaceae secondary metabolites on feeding parameters of insects by demonstrating food consumption, approximate digestibility of consumed food, efficiency of converting the ingested food to body substance, efficiency of converting digested food to body substance and consumption index was reviewed in detail. Further how the digestive enzymes including a-Amylases, α and β- glucosidases (EC 3.2.1.1), lipases (EC 3.1.1) Proteases, serine, cysteine, and aspartic proteinases affected by the Meliaceae secondary metabolites was reviewed. Further effect of Meliaceae secondary metabolites on detoxifying enzymes have been found to react against botanical insecticides including general esterases (EST), glutathione S-transferase (GST) and phosphatases was reviewed. Alkaline phosphatase (ALP, E.C.3.1.3.1) and acid phosphatase (ACP, E.C.3.1.3.2) are hydrolytic enzymes, which hydrolyze phosphomonoesters under alkaline or acid conditions, respectively. These enzymes were affected by the secondary metabolites treatment. The detailed mechanism of action was further explained in this review. Acethylcholine esterase (AChE) is a key enzyme that terminates nerve impulses by catalyzing the hydrolysis of neurotransmitter, acetylcholine, in the nervous system of various organisms. How the AChE activity was altered by the Meliaceae secondary metabolites reviewed in detail.

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Physiological and biochemical effect of neem and other Meliaceae plants secondary metabolites against Lepidopteran insects

Structural diversity and bioactivities of natural benzophenones.

Eight new monoterpenoid indole alkaloids, alstoyunines A-H (1-8), along with 17 known analogues, were isolated from Alstonia yunnanensis. The structures of. the new alkaloids were established by means of extensive spectroscopic methods. Alstoyunines C (3), E (5), and F (6) showed selective inhibition of Cox-2 (>75%). Alstoyunine F (6) showed weak cytotoxicity against the human myeloid leukemia HL-60 (IC(50) = 3.89 mu M) and hepatocellular carcinoma SMMC-7721 (IC(50) = 21.73 mu M) cell lines.

Monoterpenoid Indole Alkaloids from Alstonia yunnanensis

Three new sterols (1-3) including an unprecedented ring A-seco natural product (1), five new terpenoids (4-8), and 15 known compounds were isolated from the bark of Melia azedarach. Their structures were elucidated by means of spectroscopic data, and the structure of 1 was confirmed by X-ray crystallography.

Sterols and terpenoids from Melia azedarach.

Four new compounds named (3E,7Z,11E)-19-hydroxycasba-3,7,11-trien-5-one (1), 6 alpha-hydroxy-10 beta-methoxy-7 alpha,8 alpha-epoxy-5-oxocasbane-20,10-olide (2), 15 alpha-hydroxylup-20(29)-en-3-one (3), and (2R,4aR,8aR)-3,4,4a,8a-tetrahydro-4a-hydroxy-2,6,7,8a-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-chromene-5,8-dione (4) were isolated from the MeOH extracts of the aerial parts of Ricinus communis L. by chromatographic methods. Their structures were elucidated by extensive spectroscopic experiments.

Qin-Gang Tan

Papers

Meliaceous limonoids: chemistry and biological activities.

Monoterpenoid Indole Alkaloids from Alstonia yunnanensis

Sterols and terpenoids from Melia azedarach.

Three Terpenoids and a Tocopherol-Related Compound from Ricinus communis

Megastigmane-type Compounds from Rotala rotundifolia