Rheum australe, an endangered high-value medicinal herb of North Western Himalayas: a review of its botany, ethnomedical uses, phytochemistry and pharmacology

Abstract

Rheum australe (Himalayan Rhubarb) is a multipurpose, endemic and endangered medicinal herb of North Western Himalayas. It finds extensive use as a medicinal herb since antiquity in different traditional systems of medicine to cure a wide range of ailments related to the circulatory, digestive, endocrine, respiratory and skeletal systems as well as to treat various infectious diseases. The remedying properties of this plant species are ascribed to a set of diverse bioactive secondary metabolite constituents, particularly anthraquinones (emodin, chrysophanol, physcion, aloe-emodin and rhein) and stilbenoids (piceatannol, resveratrol), besides dietary flavonoids known for their putative health benefits. Recent studies demonstrate the pharmacological efficacy of some of these metabolites and/or their derivatives as lead molecules for the treatment of various human diseases. Present review comprehensively covers the literature available on R. australe from 1980 to early 2018. The review provides up-todate information available on its botany for easy identification of the plant, and origin and historical perspective detailing its trade and commerce. Distribution, therapeutic potential in relation to traditional uses and pharmacology, phytochemistry and general biosynthesis of major chemical constituents are also discussed. Additionally, efficient and reproducible in vitro propagation studies holding vital significance in preserving the natural germplasm of the plant and for its industrial exploitation have also been highlighted. The review presents a detailed perspective for future studies to conserve and sustainably make use of this endangered plant species at a commercial scale.

Comparative transcriptome analysis of Rheum australe, an endangered medicinal herb, growing in its natural habitat and those grown in controlled growth chambers

“…ex Meissn.) is one such species of family “Polygonaceae” that grows luxuriously in the grassy or rocky slopes of the Himalayas at an altitude of 3000–4200 m above mean sea level (amsl) across India, Nepal, and Bhutan 6 , 7 . In India, the species has been recorded from Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh 6 .…”

“…In India, the species has been recorded from Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh 6 . R. australe is a leafy perennial herb and is commonly known as “Himalayan Rhubarb” or red-veined pie plant 7 . Interestingly, in contrast to the small leaf features of many alpine herbs, R. australe exhibits an exceptionally unique broad leaf phenotype 8 .…”

“…Besides, the species yields a natural dye in cosmetics, textiles, and food industry 11 . Due to overexploitation of the species for various industrial purposes, overgrazing, habitat destruction due to human activities and shift of tree line due to climate change, the population of R. australe has shown severe depletion which brought it amongst the category of endangered plant species 7 .…”

A Song of Ice and Fire: Cold and Hot Properties of Traditional Chinese Medicines

“…The main effective components of Dahuang are anthraquinones such as emodin, emodin methyl ether, aloe emodin, rhein, chrysophanol, etc. In addition, phenolic compounds were identified including catechins, glucose gallates, naphthalenes, sennosides, and stilbenes ( Zargar et al, 2011 ; Pandith et al, 2014 ; Pandith et al, 2018 ). According to reports, the crude extracts and isolated compounds of Dahuang have a wide spectrum of pharmacological activities including antipyretic, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, anticancer, hypoglycemic, immune-enhancing, liver-protective, kidney-protective, and central neuroprotective effect ( Zargar et al, 2011 ; Kong et al, 2014 ; Esposito et al, 2016 ; Li X. et al, 2019 ).…”

Application of Natural Dyes for Herbal Textiles

“…Rheum emodi contains anthraquinones (rhein, emodin, aloe-emodin, chrysophanol, physcion, and rhein), stilbenoids (resveratrol and piceatannol), and flavonoids. UV protective effect of Rheum emodi is supposed to be due to flavonoids, which absorb the UV radiation [60]. Main coloring ingredient of the dye extracted from Gardenia yellow is crocin, which is a water soluble carotene, which absorbs the UV rays [61].…”