Darjeeling and Sikkim Himalayas, a part of Eastern Himalayan Hotspot, is characterized by its richness of plant diversity. Herbal medicine has been one of the most popular and reliable healing practices among the different ethnic groups of this region for ages. However, the lack of documentation practice by the traditional healers has led to obscurity regarding the efficacy of herbal medicine among the present generation, though they have to depend on the same quite often. Meanwhile, several reviews have attempted to document the plants used for the treatment of diabetes from this region, but interestingly, very few research works can be obtained regarding the characterization of antidiabetic properties of the plants of this region. Therefore, it demands a better understanding of the potentiality of these plants in the purview of scientific evidence. This review article reports 55 such plant species which have been reported to be frequently used in the treatment of hyperglycemia and our objective was to validate the potentiality of the plants in the light of recent phytochemical and pharmacological researches being carried out locally or elsewhere.

Angiotensin-converting enzyme (ACE) inhibitors are antihypertensive medications often used in the treatment of diabetes-related complications. Synthetic ACE inhibitors are known to cause serious side effects like hypotension, renal insufficiency, and hyperkalaemia. Therefore, there has been an intensifying search for natural ACE inhibitors. Many plants or plant-based extracts are known to possess ACE-inhibitory activity. In this review, articles focusing on the natural ACE inhibitors extracted from plants were retrieved from databases like Google Scholar, PubMed, Scopus, and Web of Science. We have found more than 50 plant species with ACE-inhibitory activity. Among them, Angelica keiskei, Momordica charantia, Muntingia calabura, Prunus domestica, and Peperomia pellucida were the most potent, showing comparatively lower half-maximal inhibitory concentration values. Among the bioactive metabolites, peptides (e.g., Tyr-Glu-Pro, Met-Arg-Trp, and Gln-Phe-Tyr-Ala-Val), phenolics (e.g., cyanidin-3-O-sambubioside and delphinidin-3-O-sambubioside), flavonoids ([-]-epicatechin, astilbin, and eupatorin), terpenoids (ursolic acid and oleanolic acid) and alkaloids (berberine and harmaline) isolated from several plant and fungus species were found to possess significant ACE-inhibitory activity. These were also known to possess promising antioxidant, antidiabetic, antihyperlipidemic and anti-inflammatory activities. Considering the minimal side effects and lower toxicity of herbal compounds, development of antihypertensive drugs from these plant extracts or phytocompounds for the treatment of diabetes-associated complications is an important endeavour. This review, therefore, focuses on the ACE inhibitors extracted from different plant sources, their possible mechanisms of action, present status, and any safety concerns.
Angiotensin-Converting Enzyme Inhibitors ; Antihypertensive Agents ; Diabetes Complications/drug therapy* ; Diabetes Mellitus/drug therapy* ; Humans ; Peptides