In vitro micropropagation, phytochemical, and antioxidant analysis of Rhynchostylis retusa (L). Blume: endangered epiphytic orchid

Rhynchostylis retusa is an ornamental blooming orchid and traditionally known for its medicinal uses. This study has examined in vitro micropropagation, phytochemical analysis, and antioxidant activity of Rhynchostylis retusa. The seeds were inoculated on three different nutrient media namely Mitra (1976), Knudson C Orchid (1946) and Murashige and Skoog (1962) medium. Mitra medium showed a better response of germination supplemented with napthalene acetic acid (1mg/l) and benzylaminopurine (1.5 mg/l). The preliminary phytochemical evaluation reveals the different secondary metabolites, including alkaloids, carbohydrates, coumarin, flavonoids, phenol, tannins, terpenoids, and quinine in methanolic extract. The total phenolic (359 µg/ml) and total tannin (275.25 µg/ml) contents were higher in the leaf than in the root. At a concentration of 300 µg/ml, ascorbic acid, leaf extract, and root extract exhibited radical scavenging activities of 87.56%, 73.28%, and 64.77%, respectively. The higher scavenging activity of the leaf extract indicates its strong ability to neutralize harmful free radicals, thereby functioning as an effective antioxidant agent. These findings suggest that the plant possesses considerable antioxidant potential and may be beneficial in mitigating disorders associated with oxidative stress. Furthermore, limonene, a phenolic compound, was identified in the methanolic extract using reverse-phase high-performance liquid chromatography (RP-HPLC). Therefore, prioritizing conservation and sustainable management of this plant is essential to preserve its unique phytochemical profile and potential therapeutic benefits.