Antioxidant And Antitumor Activities Of Phenolics From Guava(Psidium Guajava L.)

Psidium guajava is widely distributed in Guangdong, Taiwan, Guangxi, Yunnan and other provinces of China. Many studies found that guava is rich in nutrients and active substances. Besides, guava has been shown to have relatively strong anti-inflammatory, antioxidant, antibacterial, hypoglycemic, antitumor and other physiological activity. But previous studies have focused on the active ingredients and biological activities of guava leaves,the study about the active substance of the edible parts of guava has been rarely reported and much less about the comparative analysis of active ingredients of different varieties between pulp and peel. So, present work mainly explore the major functional components of domestic common guava varieties and comprehensively and systematically evaluate in vitro antioxidant and cellular antioxidant activity and anti-tumor activity.In the study, the free and bound polyphenols in peel and pulp samples of the four commom guava varieties in south China were extracted, and the contents of phenolics and flavonoids were also measured. Besides, we analysis the active phenolics in the guava extracts by HPLC. The free and bound polyphenols are extracted respectively by using 80% acetone and Na OH digestion combined with ethyl acetate extraction; And the determination of total flavonoids is using the sodium borohydride- chloranil colorimetry(SBC method). The results showed that there are obvious differences between guava peel and flesh, between different varieties in the contents of total polyphenols and total flavonoids(P<0.01). In a word, Hongxin variety was much better than Yanzhihong, zhenzhu and baiyuzhenzhu varieties, and the peel extract are significantly superior to pulp. The total phenolic contents of peel and pulp extracts of Hongxin guava were 1080.25 ± 65.33, 448.66 ± 81.4 mg galic acid/100 g FW, total flavonoid contents were 505.1 ± 6.8, 212.52 ± 7.07 mg catechin/100 g FW. HPLC spectras of different guava varieties are complex and very similar.ORAC、PSC、ABTS and FRAP assays were used as evaluation methods of in vitro antioxidant capacity, CAA as evaluation method of cellular antioxidant capacity to evaluate the antioxidant activity of guava peel and pulp extracts of different varieties designed to evaluate the antioxidant activity of guava in a more comprehensive and systematic way. The results determined by CAA and the four chemical evaluation methods are roughly the same in which the antioxidant activity of Hongxin guava extracts is the better than the other three varieties(P<0.01). The ORAC value, PSC value, ABTS value and FRAP value of Hongxin guava were: 9579.75 ± 359.06 μmol Trolox equiv / 100 g FW, 5519.29 ± 77.66 μmol Vit C equiv / 100 g FW, 5071.84 ± 39.15 μmol Trolox equiv / 100 g FW and 3152.86 ± 9.45 μmol Trolox equiv / 100 g FW; the corresponding values of its pulp were 4630.35 ± 109.72, 2354.34 ± 41.57, 2892.99 ± 11.03 and 1525.48 ± 20.31. The CAA values of the peel and pulp extracts in the cases of No PBS wash and PBS wash were 1241.9 ± 113.46, 310.48 ± 25.34(No PBS wash) and 258.73 ± 20.67,74.99 ± 6.78(PBS wash) μmol of quercetin equiv./100 g FW. But there are some differences in the order of four guava varieties among the five methods. And there are significant correlations between the contents of total phenolic and total flavonoids of guava extracts and the antioxidant values determined by the five methods(r2>0.8).Cytotoxicity and anti-proliferative avtivitity of guava extracts on Hep G2, MCF-7 and MDA-MB-231 cells were evaluated by Methylene method.The results showed that peel and pulp extracts of four guava varieties have significantly inhibited the proliferation of the three cancer cells and toxicity test proved samples non-toxic and among the three ancer cells, the anti-proliferative effect on Hep G2 cells of guava extracts is the strongest. In four guava varieties, the EC50 value of Hongxin guava is the minimum, the EC50 value of peel extract on Hep G2, MCF-7 and MDA-MB-231 cells were 4.47 ± 0.4, 8.03 ± 0.45 and 8.26 ± 0.33 mg/ml. The EC50 value of flesh extract were 10.97 ± 0.87,16.75 ± 0.42 and 21.78 ± 0.23 mg/ml. Besides, there are significant correlations between the contents of total phenolics and total flavonoids and the EC50 values of antiproliferation of guava extracts on Hep G2, MCF-7 and MDA-MB-231cells(r2>0.8).