G. Suresh

Two new cytotoxic labdane diterpenes from the rhizomes of Hedychium coronarium

The phytochemical investigation of the hexane extract of the Hedychium coronarium led to the isolation and identification of two new labdane diterpenes (1 and 2) along with 10 known metabolites (3-12). The structures of the new compounds were established on the basis of spectroscopic data analysis (1D and 2D NMR and MS). Cytotoxic activities of the isolates were studied against the A-549 (lung cancer), SK-N-SH (human neuroblastoma), MCF-7 (breast cancer) and HeLa (cervical cancer) cell lines.

Synthesis of antihyperglycemic, α-glucosidase inhibitory, and DPPH free radical scavenging furanochalcones

A series of furanochalcone derivatives have been designed and synthesized. Molecular modeling studies were carried out to probe into the mechanism of binding of chalcone inhibitors and understand the structure–activity relationship to identify the contribution of scaffolds and groups in the synthesized analogs to biological activity. The three-dimensional model of α-glucosidase was constructed based on the crystal structure family 31 α-glycosidase (PDB 1XSI) using Modeller9v5. Docking of the inhibitors on the built homology model revealed interactions in the active site region mostly with Asp 252, Tyr254, Gln523, and Arg571. 2D-QSAR models were generated with CODESSA using Heuristic method. The best predictive model was generated using three descriptors that gave a correlation co-efficient (r2) 0.9886 and cross-validate (r2) 0.9338. The synthesized compounds were screened against the α-glucosidase inhibition and DPPH radical scavenging properties. All the synthetic compounds displayed varying degrees of α-glucosidase inhibitory and DPPH scavenging activities. Compound 8c was found most potent α-glucosidase inhibitor though; it could not display DPPH scavenging activity. When tested in vivo for antihyperglycemic activity in starch-loaded Wistar rats, 8c was equally effective in reducing time-dependent hyperglycemia as to the standard drug, Acarbose. Compound 8c may serve as an interesting compound for the development of therapeutics targeted against diet-induced hyperglycemia in diabetes.

Limonoids from the leaves of Soymida febrifuga and their insect antifeedant activities.

Three new phragmalin-type limonoids (1-3) were isolated from the leaves of Soymida febrifuga together with thirteen known limonoids. The structures of these compounds were established on the basis of spectroscopic data. All these isolates were evaluated for their anti-feedant activities in tobacco caterpillar (Spodoptera litura) and castor semilooper (Achaea janata) using a no-choice laboratory bioassay. Among the tested, compounds 9 and 15 demonstrated the potent anti-feedant index (76.46 μg/cm(2), 66.61 μg/cm(2) against A. janata, and 61.69 μg/cm(2), 51.93 μg/cm(2)against S. litura).

Cytotoxic sesquiterpenes from Hedychium spicatum: isolation, structure elucidation and structure-activity relationship studies.

Phytochemical investigation of chloroform extract from rhizomes of Hedychium spicatum resulted in the isolation of six new sesquiterpenes (1-6) along with fifteen known compounds (7-21). Their structures were elucidated on the basis of the extensive spectroscopic analyses (IR, Mass and NMR) and by comparison of the data with those reported in the literature. Further, cytotoxic activities of all the isolates were evaluated by determining their inhibitory effects against A-549, B-16, Hela, HT-29, NCI-H460, PC-3, IEC-6 and L-6 cancer cell lines. Results indicated that compounds 1 and 3 may serve as an important natural lead compounds for future development as they showed potent cytotoxic activity against Hela cell lines with an IC50 value of 0.3 μg/mL and 1.80 μg/mL, respectively.

Synthesis and insect antifeedant activity of plumbagin derivatives

Napthaquinones have received considerable interest in agricultural chemistry because of a novel action mode, extremely high activity against a broad spectrum of insects, low acute toxicity to mammals, and environmentally benign characteristics. A series of plumbagin derivatives (3a–3o) were synthesized under mild esterification conditions in straightforward procedure. The structures of all new compounds were confirmed by NMR, IR, MS, and HREIMS analyses. The plumbagin derivatives were screened for their insecticidal activities against tobacco caterpillar (Spodoptera litura) and castor semilooper (Achaea janata) using a no-choice laboratory bioassay. The results show that some of the title compounds exhibit excellent antifeedant activities against 3rd instar larvae of A. janata and S. litura. The improvement in antifeedant activity requires a reasonable combination of substituents in the parent structure, which provides some hints for further investigation on structure modification.Graphical AbstractA series of plumbagin derivatives (3a–3o) were synthesized under mild conditions and screened for their insecticidal activities against tobacco caterpillar (Spodoptera litura) and castor semilooper (Achaea janata) using a no-choice laboratory bioassay.

New advanced glycation end-products inhibitors from Dichrostachys cinerea Wight & Arn.

Free radical scavenging and advanced glycation end-product (AGE) inhibitory potential were evaluated in the crude methanol extract of Dichrostachys cinerea. Bioassay-guided isolation led to the identification of four flavan-3-ols, namely (−)-mesquitol (1), oritin (2), (−)-festidinol (3) and (−)-epicatechin (4). Analysis of structure–activity relationships revealed that the presence of 7,8-dihydroxyl groups in the A-ring of flavan-3-ols in conjunction with 3′,4′-dihydroxyls in the B-ring (1) is an important criterion for displaying potent AGE inhibitory activity along with free radical scavenging properties. (−)-Mesquitol (1), oritin (2), and (−)-festidinol (3) were found to be new natural AGE inhibitors. (−)-Mesquitol (1) displayed the most potent AGE inhibitory activity. Results suggest that (−)-mesquitol (1) may serve as an important natural organic lead compound for future development of antiglycating agents along with potent antioxidant activity.