Composition And Function Of Anthraquinone Components From Juemingzi (Cassia Tora L.)

Juemingzi is the seeds of the legume Cassia tora L. or Cassia obtusifolia L.. Juemingzi is an important medicinal origin plant, which is well known to have pharmacological activities such as diuretic, diarrhea and antihypertension that have been conventionally used as healthy beverage with many people from ancient time. Anthraquinones are the main functional components in juemingzi. Modern research showed that anthraquinone has multi-functions including antibacterial, antioxidant and antimutagen. In this work, systematic experiments were carried out on extraction and identification of anthraquinone profile in juemingzi. Furthermore, the physiological activity of anthraquinone was evaluated preliminarily.The anthraquinones constituents in the seed of Cassia tora L. were investigated. The constituents were isolated through column chromatography. Their structures were elucidated through physiochemical and spectral analysis. Nine anthraquinones were isolated and identified as chrysophanol (1), physcion (2), 8-methoxy-chrysophanol (3), emodin (4), chryso-obtusin(5), 8-methoxy-emodin(6), 2-methoxy-chrysophanol-8-O-β-D- glucopyranoside (7), 4,6,7-trimethoxy-aloe-emodin-8-O-β-D-glucopyranoside (8) and emodin-6-O-β- gentiobioside (9). Among them, compounds 3, 6, 7, 8 and 9 were obtained from this plant for the first time.The extraction and isolation of anthraquinones in juemingzi with reflux method were studied. The optimal condition was 70% ethanol (V:V), the ratio of solid to liquid (1:20), extraction 4 hours, 50℃by single factor and orthogonal experiments. The anthraquinones were isolated from crude extracts with 0.5% alkaline solution and 1:15 the ratio of solid to liquid, then deposited at pH2. The content of anthraquinone was 65.4%. Effect of heating treatment on anthraquinone in juemingzi was evaluated. Total content of anthraquinones changed little. The free anthraquinone increased, and anthraquinone glycoside decreased. The above results indicated that glycoside bond of anthraquinone were degraded by thermal treatment.The antioxidant properties of free anthraquinones obtained from juemingzi were evaluated using a variety of in vitro methods including reducing power, peroxidation of linoleic acid and low density lipoprotein (LDL) and chelating effect on transitional ions. The results showed that all anthraquinones tested could reduce peroxidation of linoleic acid induced by AIBN. Based on the UV-visible scanning spectra of anthraquinones, it was speculated that anthraquinones scavenge free radicals in two different manners.