Chemical Constituents Of Hemp Seed And Their Biological Activities

Cannabis sativa, an important economic and medicinal plant, originating from central Asia, is cultivated widely in the world, and includes mainly two susspecies in China. Hemp seed, the dry mature seeds of C. sativa ssp. sativa var. sativa, also named maziren, is a typical edible and pharmaceutical product. Because of its rich vegetable protein, dietary fiber and polyunsaturated fatty acids, hemp seed is widely used in foods and animal feeds. Lubricant and laxative effects of hemp seed are recorded in Chinese Pharmacopoeia. It was also reported that hemp seed had antioxidant, anti-aging, antihypertensive, anti-platelet aggregation and antibacterial effects, and was potent against neurodegenerative diseases. It’s necessary to further study its chemical constituents.In this work, from an ethanol extract of hemp seed,24 compounds were isolated by repeated column chromatography and semipreparative high-performance liquid chromatography (HPLC). Their structures were established on the basis of mass spectrum, nuclear magnetic resonance (’H-NMR,13C-NMR, HSQC, HMBC and COSY), IR, UV and circular dichroism (CD) analysis. The obtained compounds include 2 fatty acid glycerol ester:1-mono-palmitin (1),9,12-Octadecadienoic acid (24); four alkaloids:(12R)-Neoechinulin A (2a), (12S)-Neoechinulin A (2b), (12R)-Dihydroxyisoechinulin A (19), (12S)-Dihydroxyisoechinulin A (20); fifteen lignanamides:Cannabisin E (3), Isocannabisin E (4), Cannabisin M (6), Grossamide (7), (2,3-trans)-3-(3-hydroxy-5-methoxyphenyl)-N-(4-hydroxyphenethyl)-7-{(E)-3-[(4-hydroxyph-enethyl)amino]-3-oxoprop-1-enyl}-2,3-dihydrobenzo [b] [1,4]dioxine-2-carboxamide (8), Cannabisin N (9), Cannabisin F (10), N-trans-caffeoyltyramine (11), Cannabisin O (12), Cannabisin A (13),3,3’-Demethylheliotropamide (14), N-tram-feruloyltyramine (15), Cannabisin C (16),3,3’-Demethyl grossamide (21), Cannabisin D (22) and four others:trans-p-Hydroxycinnamic acid (5), 4-Methoxy-3H-benzofuran-2-one (17),p-hydroxybenzaldehyde (18). Among them,4, 6,9,12,14 and 19 are new compounds, and compounds 2a,2b,17,18,20 and 23 were isolated from hemp seed for the first time. The biosynthetic pathway and configuration of lignanamides were discussed based on literatures. The antioxidant, acetylcholinesterase (AChE) inhibitory, SIRT1 (silent information regulator 1) regulation activities and quinone reductase inducing activity of some compounds were evaluated. Most of the tested compounds exhibited good antioxidant activity. 3,3’-Demethylheliotropamide and 3,3’-Demethyl grossamide showed AChE inhibitory activity. Initial screening suggested Neoechinulin A could upregulate the expressions of SIRT1 in HEK293 cell. None of the tested compounds showed quinone reductase inducing activity. In addition, since the compounds like 2a,2b,19,20 are often reported from the matabolites of fungi such as Aspergillus or Eurotium, and rarely reported from plants, the origin of these compounds was further tracked and the results showed that this kind of compounds are indeed the chemical constituents of the hemp seed instead of fungal metabolites.