Author
A. K. Sarkar
Bio: A. K. Sarkar is an academic researcher from Botanical Survey of India. The author has contributed to research in topics: Chromosome (genetic algorithm). The author has an hindex of 2, co-authored 2 publications receiving 42 citations.
Topics: Chromosome (genetic algorithm)
Papers
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37 citations
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TL;DR: Moscatilin, a new bibenzyl derivative isolated from the orchid Dendrobium moscatum, was shown to have the structure 4,4′-dihydroxy-3,3′,5-trimethoxybibensyl.
81 citations
TL;DR: Flavanthrin, the first dimeric 9,10-dihydrophenanthrene derivative, was isolated from the orchid Eria flava which also yielded the previously reported 9, 10-dibhrenanthrene coelonin this paper.
54 citations
TL;DR: Major antioxidant stilbenoids (1–3) from Vanda coerulea stems displayed an inhibition of UVB-induced COX-2 expression and could be potentially used for skin protection against the damage caused by UVB exposure.
Abstract: Background
In our investigations towards the isolation of potentially biologically active constituents from Orchidaceae, we carried out phytochemical and biological analyses of Vanda species. A preliminary biological screening revealed that Vanda coerulea (Griff. ex. Lindl) crude hydro-alcoholic stem extract displayed the best DPPH /•OH radical scavenging activity and in vitro inhibition of type 2 prostaglandin (PGE-2) release from UVB (60 mJ/cm2) irradiated HaCaT keratinocytes.
Principal Findings
Bio-guided fractionation and phytochemical analysis led to the isolation of five stilbenoids: imbricatin (1) methoxycoelonin (2) gigantol (3) flavidin (4) and coelonin (5). Stilbenoids (1–3) were the most concentrated in crude hydro-alcoholic stem extract and were considered as Vanda coerulea stem biomarkers. Dihydro-phenanthropyran (1) and dihydro-phenanthrene (2) displayed the best DPPH/•OH radical scavenging activities as well as HaCaT intracellular antioxidant properties (using DCFH-DA probe: IC50 8.8 µM and 9.4 µM, respectively) compared to bibenzyle (3) (IC50 20.6 µM). In turn, the latter showed a constant inhibition of PGE-2 production, stronger than stilbenoids (1) and (2) (IC50 12.2 µM and 19.3 µM, respectively). Western blot analysis revealed that stilbenoids (1–3) inhibited COX-2 expression at 23 µM. Interestingly, stilbenoids (1) and (2) but not (3) were able to inhibit human recombinant COX-2 activity.
Conclusions
Major antioxidant stilbenoids (1–3) from Vanda coerulea stems displayed an inhibition of UVB-induced COX-2 expression. Imbricatin (1) and methoxycoelonin (2) were also able to inhibit COX-2 activity in a concentration-dependent manner thereby reducing PGE-2 production from irradiated HaCaT cells. Our studies suggest that stilbenoids (1–3) could be potentially used for skin protection against the damage caused by UVB exposure.
48 citations
TL;DR: The structure of 3′- O -methylbatatasin III, a new bibenzyl of the East Himalayan orchid, Coelogyne ovalis, has been established on the basis of spectral and chemical data.
43 citations
TL;DR: In this paper, Reptanthrin and isoreptanthrin, two new dimeric phenanthrenes, were isolated from the orchid Bulbophyllum reptans which also afforded nine known stilbenoids, viz.
41 citations