Abstract
Actinomycete endophytes (135) were isolated from Cajanus lineatus W. & A. (Maesen), Leucas ciliata Benth., Rauwolfia densiflora Benth. Ex. Hook. f. and Gomphostemma heyneanum Wall., four ethnomedicinal species of the southern region of the Western Ghats, a hot spot of biodiversity. The isolates were categorized into three supra generic groups on the basis of spore or aerial mycelial characters and confirmed by the partial 16S rRNA gene sequences. The actinomycete strains were subjected to fermentation and the ethyl acetate extracts were screened for the antioxidant assays. Streptomyces globosus (JQ926176) and Arthrobacter sp. (JQ926171) isolated from the stem fragments of R. densiflora and L. ciliata showed remarkable dose-dependent antioxidant activity in the in vitro assays. Among the screened extracts, S. globosus (IC50 88.2±1.03 μg/ml) and Arthrobacter sp. (IC50 = 97.6±1.97 μg/ml) exhibited high DPPH activity. S. globosus and Arthrobacter extracts contained a total antioxidant activity of 52.44±2.03 μM Fe (II)/g and 40.44±1.97 μM Fe (II)/g respectively. A significant correlation between the total phenolic content and total reducing power of S. globosus (R2=0.983) and Arthrobacter sp. (R2=0.987) extracts were noted. GC-MS characterization of the extracts revealed several compounds with antioxidant activity. S. globosus, S. hypolithicus, P. citrea and P. minatonensis are reported as endophytes for the first time in the ethnomedicinal plants.
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