Summary
The anthraquinone emodin, identified in 17 plant families distributed worldwide, has numerous biological activities, some of which exhibit a wide spectrum of ecological impacts by mediating biotic or abiotic interactions of plants with their environment. Here the evidence for direct and indirect effects of emodin on plant survival and reproduction is reviewed. Emodin in vegetative organs may help protect plants against herbivores, pathogens, competitors and extrinsic abiotic factors (e.g. high light intensities). In unripe fruit pulp, emodin may facilitate seed dispersal by protecting the immature fruit against predispersal seed predation whereas in ripe pulp it may deter frugivores and thus reduce the chances that seeds will be defecated beneath the parent plant. It also accelerates the passage of seeds through the digestive tract, potentially reducing dispersal distance and increasing seed viability upon dispersal. In certain circumstances both of the last two effects could also have negative fitness consequences for plants. Natural selection should favor secondary metabolites with multiple functions because they protect the plants against a variety of unpredictable biotic and abiotic environments. Such metabolites also enhance plant defenses by using different molecular targets of specific enemies through a variety of mechanisms of action. Emodin illustrates the wide and often overlooked potential for chemical multifunctionality in plant secondary metabolites.

Emodin--a secondary metabolite with multiple ecological functions in higher plants.

Antioxidant activities of flavidin in different in vitro model systems.

Flavidin was isolated from Orchidaceae species and puriﬁed by silica gel column chromatography. The structure was
identiﬁed using physical and spectral (1H, 13C NMR, and mass) data. Antioxidant potency of ﬂavidin was investigated employing various established in vitro model systems viz., b-carotene-linoleate, 1,1-diphenyl-2-picryl hydrazyl (DPPH), phosphomolybdenum method, and scavenging of hydrogen peroxide methods. Flavidin showed very good antioxidant activity (90.2%) and almost equivalent
to that of BHA at 50ppm level by b-carotene-linoleate method. Radical scavenging activity of ﬂavidin was compared with BHA at 5, 10, 20, and 40ppm concentration and ﬂavidin showed more radical scavenging activity than BHA at all the tested concentrations. Furthermore, ﬂavidin showed very good antioxidant capacity by the formation of phosphomolybdenum complex method. Besides this, ﬂavidin showed effective hydrogen peroxide scavenging activity. The data obtained in the in vitro models clearly establish the antioxidant potency of ﬂavidin. However, comprehensive studies need to be conducted to ascertain the in vivo safety of ﬂavidin in experimental animal models. This is the ﬁrst report on antioxidant activity of 9,10-dihydro-5H-phenanthro-(4,5 bcd)-pyrans/ﬂavidin type of compounds.

Antioxidant activities of ﬂavidin in diﬀerent in vitro model systems

Pyranonaphthoquinone antibiotics--isolation, structure and biological activity.

The fresh or dried stems of many Dendrobium species are well known as one of the most expensive tonics in traditional Chinese medicine Documented as a “superior grade” herbal medicine in the ancient text “Shen Nong’s Herbal Classic”, Dendrobium has been used for thousands of years and is now a popular health food worldwide The main chemical components of Dendrobium are alkaloids, aromatic compounds, sesquiterpenoids and polysaccharides, with multiple biological activities, including immunomodulatory, neuroprotective and anti-tumor effects, etc Various qualitative and quantitative methods have been developed for the quality evaluation of Dendrobium In this review, the research progress since the 1930s relating to the chemistry, bioactivity and quality control of Dendrobium is summarized, existing problems and prospects are also discussed

K.V.Jagannadha Rao

Papers

Bibenzyls and phenanthrenoids of some species of orchidaceae

Benzisochromanquinones fromVentilago goughii

Amoenumin, A 9,10-dihydro-5H-phenanthro-(4,5-b,c,d)-pyran from Dendrobium amoenum

An acetonaphthone and an isofuranonaphthoquinone from Ventilago goughii

Quinones and tetracosanolide in Ventilago bombaiensis