Author(s):

Swagata Nag and Suman Kumaria

Abstract: Vanda coerulea Griff ex. Lindl. is an endangered epiphytic orchid with various medicinal usages in traditional medicines. Different phytochemicals such as flavidin, imbricatin, coelonin, methoxycoelonin, gigantol have been reported to be present in V. coerulea. An attempt has been made in the current study to enhance the in vitro production of phytochemical constituents by the application of chitosan, a biotic elicitor which may reduce the pressure on its unmindful collection from wild. In vitro cultures of V. coerulea were raised via asymbiotic seed germination on B₅ medium. Highest number of PLBs which give rise to full grown plantlets was achieved in B₅ medium supplemented with 3µM thidiazuron. The effect of chitosan both on plantlet development and enhancement of phytochemical constituents was studied. The present study revealed that chitosan at 4 mg/l in the medium benefited the accumulation of the secondary metabolites, and greatly affected both the antioxidant as well as PAL enzyme activities. There was an increase of flavonoid and alkaloid contents by 2.3 and 4.17 fold in the methanolic leaf extract as compared to the control. However, the highest total phenolic and tannin contents were found in chloroformic leaf extract with 3.07 and 2.57 fold increases, respectively. The PAL activity of treated sample was found to be 5 fold higher compared to the untreated sample. A significant higher yield of antioxidant activities was observed after exogenous application of chitosan. The present investigation suggests that chitosan may have triggered the metabolic pathway in treated V. coerulea plantlets by inducing the PAL enzyme activity through the enhancement of various phytochemicals such as phenolics, alkaloids and flavonoids, which potentially reported to impart the medicinal value to the plant.

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