Research progress on pharmacological activity and pharmacokinetics of capsaicin
Capsicum annuum L. is a perennial herbaceous plant of the Magnoliaceae family, belonging to the genus Capsicum. It is widely used as a medicinal and edible plant worldwide. The medicinal part is the fruit, which has the effects of warming the middle and dispelling cold, reducing qi and promoting digestion. Chili peppers contain various active ingredients such as capsaicin, chili esters, and carotenoids. The capsaicin family mainly includes capsaicin, dihydrocapsaicin, high capsaicin, high dihydrocapsaicin, low dihydrocapsaicin, capsaicin esters, dihydrocapsaicin esters, low dihydrocapsaicin esters, capsaicin – β – D-glucopyranose glycosides, dihydrocapsaicin – β – D-glucopyranose glycosides, etc. (see Figure 1). Capsaicin is a high content and pungent ingredient in chilli, which has a wide range of pharmacological effects such as analgesia, anti-oxidation, myocardial protection, anti-tumor, thermogenesis, weight loss and so on. Some of the pharmacological effects depend on the transient receptor potential vanilloid 1 (TRPV1). For example, in July 2020, Avericas Pharma’s Quenza (capsaicin) 8% patch has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of neurological pain related to adult foot diabetes peripheral neuropathy (DPN) and relief The duration is up to 3 months, which is a milestone event after the treatment of neuralgia related neuropathic pain in 2009.
In addition, capsaicin esters in the capsaicin family have similar pharmacological activities, but do not have spicy irritants. This suggests that the shortcomings of capsaicin itself can be overcome by searching for or synthesizing capsaicin analogs, which is beneficial for the development of new generation capsaicin drugs. This article reviews the structure, pharmacological activity, and metabolic kinetic properties of capsaicin.

Chili is a medicinal and edible plant, rich in a large number of capsaicin family components, and has been widely consumed worldwide for a long time. The components of the capsaicin family have attracted the interest and widespread attention of chemists, pharmacologists, and biologists. Capsaicin is widely used as a local painkiller, and research has shown that it has a wide range of pharmacological effects in antioxidant, anti-tumor, gastrointestinal diseases, and obesity inhibition. The pharmacological activity of capsaicin is closely related to its pharmacokinetic properties such as dosage, route of administration, and half-life in different tissues. Its dual effects on tumors and gastrointestinal ulcers are closely related to the dosage of administration. Low doses of capsaicin have good therapeutic effects in preventing and treating gastric ulcers. The longer metabolic half-life of capsaicin on the lungs and skin means that its effects on the lungs or skin will be better. However, the main challenges faced by systemic medication are the metabolic instability and short half-life of capsaicin, and there are currently no oral or systemic injectable capsaicin drugs on the market. The analysis of the physicochemical properties, biological activity, and metabolic kinetics of capsaicin like structures suggests that the development direction of the new generation of capsaicin is to use structural modification or search for other similar components of the capsaicin family to overcome issues such as short half-life of capsaicin; Synthesize analogs of capsaicin and study their activity and pharmacokinetics, analyze their structural activity and structure property relationship, and ultimately obtain capsaicin analogs with minimal side effects, strong activity, and long half-life. Therefore, developing structurally novel capsaicin analogs may be the direction of research for the new generation of capsaicin drugs.