In-Depth Assessment of Rhubarb, Rheum L.: A High-Value Medicinal Plant Species in the Indian Himalayan Region

The genus Rheum L. commonly known as ‘Rhubarb’ is a native of Europe, tropical to temperate Asia, and comprises of 60 species distributed worldwide. In the India Himalayan Region (IHR) eight species of Rheum have been identified. High medicinal efficacy of the diverse bioactive secondary metabolite has made Rheum one of the most sought-after genus in IHR. The communication comprehensively reviews the current knowledge and research gaps concerning the Rheum species. The review covers various aspects such as ecology, traditional medicinal uses, phytochemistry, trade, and threats the species face in the IHR. The distribution of Rheum species in IHR varies by state, Uttarakhand has the highest number of species (6), followed by Sikkim (5), Himachal Pradesh, Jammu and Kashmir, and Ladakh (4 species each), and Arunachal Pradesh (2). Since antiquity, the species have been used for over 50 different culinary and medicinal practices in IHR. A variety of bioactive phytochemicals are responsible for the medicinal properties attributed to Rheum species. Owing to the exceptional medicinal and therapeutic properties and growing demands, the species are under severe threats such as premature harvesting, illegal trade, unscientific and unorganized harvesting, and other anthropogenic pressures. It has been established that most Rheum species are threatened as per regional assessments in IHR, raising a high conservation concern. Thus, owing to endemicity, restricted distribution, and lack of information on population status and market, in-situ conservation viz., delineation of high conservation value areas and ex-situ conservation like gene banks, germplasm, cryopreservation, botanical gardens for their sustainable utilization is suggested.