3,4,5-trimethoxycinnamic acid, aka sinapinic acid methyl ether, is a naturally occurring derivative of cinnamic acid. It is very closely related in structure to sinapinic acid, ferulic acid, and caffeic acid. It is also a major metabolite of elemicin. It is part of a class of phytochemicals known as cinnamates or cinnamic acids, originally isolated from cinnamon (Cinnamomum spp).
3,4,5-trimethoxycinnamic acid has been isolated from Polygala tenuifolia, a Chinese traditional medicine which is used as a nutritional supplement or nootropic. It has also been found to occur naturally in black pepper (Piper nigrum), and has been isolated from other natural sources. Like other cinnamic acids, 3,4,5-trimethoxycinnamic acid is widespread in nature. It may have uses in naturopathic medicine, such as anxiolytic, antidepressant, and neuroprotective activity. It acts on the GABA receptors in the brain and stimulates the release of GABA.
3,4,5-trimethoxycinnamic acid may be effective for reducing acidic gastric lesions in mice, or preventing stomach ulcers. One study has also found 3,4,5-trimethoxycinnamic acid to reduce or relieve opiate withdrawal caused by morphine.
Available as the free acid, and trans isomer only.