Spatial and species-specific variation in the nutritional value and therapeutic qualities of a fern genus Diplazium in the Indian subcontinent

• Edible species of Diplazium might also have medicinal property and bioactive compounds. • Nutritional value of Diplazium was often reported higher than other local leafy vegetables. • In India, antioxidant activity of D. esculentum (DE) was found maximum from western Himalaya (WH). • Maximum Carbohydrate and fat in DE were from northeast Himalaya while protein and fiber from WH. • The protein, fat, calcium, sodium, and iron content were reported higher in D. maximum than DE. Diplazium , a widely distributed genus, has been used for edible and medicinal purposes since ancient times. The present study meta-analysed the spatial and species-specific variation in the nutritional value in terms of macro- or micronutrients, the scavenging capability against active radicals, phenolic content and antimicrobial activity of its species, collected from different regions of India based on the available published literatures. Although this genus has been extensively referenced in the literature, this study included only those research articles that provided quantitative and qualitative information about the phytochemical constituents of different edible Diplazium species from Indian regions. A Literature survey clearly indicated that the detailed information about the Diplazium species other than D. esculentum (Retz.) Sw. is limited, despite of the fact that sometimes, the nutritional value of those species has been reported higher than D. esculentum. Concurrently, the maximum information on Diplazium was available from the eastern Himalayas and least from southern India. Diplazium could be a good source of macronutrient along with minerals, Vitamin C and flavonoids. The presence of adequate phenolic content could be directly correlated with its antioxidant and antibacterial properties. Simultaneously, the nutritional components in Diplazium species in terms of protein, minerals and Vitamin C were also reported to be higher than several other local herbaceous leafy vegetables. Thus, there is a need to enhance its commercialization, so, it can be a part of the healthy diet of the mass population beyond the local communities, not only in India but also worldwide.