Study On The Antioxidant Activity And Antioxidant Mechanism Of Phenolic Compounds From Tea Seed Oil

Tea seed oil is obtained from the seeds of tea (Camellia Sinensis O’Ktze),contains many biologically active compounds including polyphenols, flavonoids andvitamins. China’s Ministry of Health has certified it as a new resource food in2009.Praised as ‘Oriental Olive Oil’, tea seed oil contains up to80%unsaturated fatty acid,but had a storage stability that was similar to olive oil, and it was shown to enhancethe shelf life of sunflower oil by a5%level, indicating a natural antioxidant effect.The hypothesis that minor components such as phenolic compounds could play amajor role in the antioxidant effects of tea seed oil has gradually been increasing. Inthis work, we attempted to elucidate the ultimatemechanism through which tea seedoil-derived phenols might contribute to these antioxidant properties.Firstly, the effect of four extraction methods(organic solvent extraction,mechanical pressing, aqueous extraction and aqueous enzymatic extraction) on thequality of tea seed oil based on active components and antioxidant capacity wasstudied. Results showed that the tea seed oil extracted by aqueous enzymaticextraction exhibited high level of active compounds and the strongest antioxidantactivity. Increasing in temperature, polarity of the solvent or especially the use ofalkali during processing resulted in a decrease in the total phenolic content andantioxidant capacity of the extracted oils. Moreover, the correlation analysis revealedthat the presence of phenolic compounds was significantly correlated with theantioxidant capacity of tea seed oil.Meanwhile,28tea seed cultivars from Anxi county of Fujian province wereanalyzed based on their active components and antioxidant capacity, providingfundamental data for authentication. The results demonstrated that the tea seed oilfrom the cultivar of Moxiang (MX), Huangqi (HQ), Xianghuaqizhong (XHQZ),Taibei-12#(TB) and Huangguanyin (HGY) do not display significant antioxidantcapacity when compared with other samples in our study. Whereas, the cultivars ofBenshan(BS), Keshanzhong (KSZ), Caicong (CC), Xiayangcaicha (XYCC), Chiye (CY), Jinguanyin (JGY), Qigaixian (QGX), Qingxinqilan (QXQL), Daye-oolong(DYOL), Xiping-tieguangyin (XPTG), Taoren (TR), Fuqiancaicha (FQCC) andHuangdan (HD) showed to possess high rates of total phenols, total flavonoids. Theyalso scored well for DPPH and ORAC value, making them good candidates forproducing tea seed oil with nutritional value. Moreover, Pearson correlation analysisshowed that the presence of phenolic compounds in tea seed oil were responsible forits individual antioxidant capacity.Furthermore, investigations were performed to identify and quantity the mostrepresentative phenolic compounds present in tea seed oil by means of HPLC. Basedon standards, thirteen phenolic compounds were isolated and indentified in extracts oftea seed oil, including caffeic acid, p-coumaric acid, benzoic acid, kaempferol,(4-hydroxyphenyl)acetic acid, Epigallocatechin, catechin, Epicatechin,Epigallocatechin gallate, Epicatechin gallate, rutin, quercetin, gallic acid. Amongthem, kaempferol was the main compound in tea seed oil, with the content of19.13μg/g.Based on the research, the extract could be isolated and purified by silica gel andSephadex LH-20. Moreover, we also investigated the antitumor effect of phenoliccompounds to determine the relationship between the chemical nature and theconcentration of individual phenolic compound and the ability to decrease humanhepatocarcinoma cancer cell viability. Results demonstrated that flavone and catechincompounds were the major compounds in tea seed oil had a significantly strongability to alter cell viability, especially for the rutin and quercetin.