Comparative analysis of root-derived ethanolic extracts from tissue-cultured vs. wild Grammatophyllum speciosum: antioxidant and antibacterial activities
Abstract
Background: Grammatophyllum speciosum, the world’s largest orchid, contains diverse phytochemicals with therapeutic potential. While antioxidant and antibacterial properties of aerial parts have been studied, comparative analysis of root extracts from wild versus tissue-cultured plants is lacking.
Objectives: This study aimed to compare antioxidant and antibacterial activities of ethanolic root extracts from wild and salt stress tissue-cultured G. speciosum, focusing on key phytochemicals.
Methods: Ethanol extraction (sonication, centrifugation, vacuum concentration) was performed on roots. Highperformance liquid chromatography (HPLC) quantified catechin, coumaric acid, vitexin, and isovitexin. Antioxidant capacity was assessed via DPPH assay (vitamin C equivalents), and antibacterial activity was evaluated using agar disc-diffusion against plant and human pathogens.
Results: HPLC revealed distinct phytochemical profiles: wild roots contained catechin (absent in tissue-cultured roots), while tissue-cultured roots uniquely expressed isovitexin and vitexin. Antioxidant activity was significantly higher in tissue-cultured roots (4.5 ± 0.2 mg/g vitamin C equivalents) compared to wild roots (2.5 ± 0.3 mg/g). Tissue-cultured extracts inhibited all tested pathogens (inhibition zones: 8–14 mm at 1 mg/mL), including Xanthomonas oryzae, Xanthomonas citri, Erwinia carotovora, Ralstonia solanacearum, Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, whereas wild root extracts showed no activity.
Conclusion: This study demonstrates that tissue-cultured roots of G. speciosum under salt stress yield extracts with superior antioxidant and broad-spectrum antibacterial properties, linked to specific phytochemicals. This supports tissue culture as a sustainable approach to enhance bioactive compounds in threatened orchids, potential cosmeceutical and agricultural applications.
