Morphoanatomical and phytochemical traits of the terrestrial orchid Calanthe masuca with antioxidant activity

Abstract

Calanthe masuca (D. Don) Lindl., a member of the family Orchidaceae, is native to Madagascar and tropical to subtropical Asia and is traditionally recognized for its therapeutic potential. Despite this, scientific evidence supporting its medicinal value remains limited. The present study aims to provide a comprehensive evaluation of the anatomical characteristics, phytochemical composition, and antioxidant potential of different parts of C. masuca, including leaves, pseudobulbs, and roots. Microscopic examination of the vegetative parts revealed distinct anatomical adaptations. Notably, both raphide and prismatic calcium oxalate crystals were observed simultaneously in the leaf tissues, serving as valuable diagnostic markers. The leaf sheath exhibited a rare discontinuous sclerenchymatous layering, indicating a unique form of structural reinforcement. The pseudobulb anatomy revealed vascular bundles encased in lignified sclerenchymatous cells, a feature rarely reported in orchids. Additionally, the root structure exhibited polyarch xylem and idioblasts containing raphides, signifying specialized adaptations to its terrestrial habitat. Qualitative phytochemical screening of ethanolic extracts from the leaves, pseudobulbs, and roots confirmed the presence of multiple bioactive constituents. Quantitative analysis exhibited significant levels of total flavonoids and phenolic content in the ethanolic leaf extract. Antioxidant activity assessed by DPPH radical scavenging was strongest in leaf extracts with the lowest IC50 value, followed by pseudobulbs and roots. These results highlight the notable anatomical specializations and rich phytochemical profile of C. masuca, underscoring its pharmacological potential, validating its traditional medicinal use, and its potential future applications in phytotherapy.