The purpose of this study was to evaluate the antioxidant and hepatocyte protective effects of guava (Psidium guajava L.) leaves cultivated in Korea. The contents of the total polyphenol of the extract was 271.57 mg gallic acid equivalent (GAE)/ g residue. Antioxidant activities of leaf extract were evaluated by examining the free radical scavenging ability. 2,2'-azinobis-( 3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and α-α-diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging activities of the extract were 1133.23 mg trolox equivalent antioxidant capacity (TEAC)/g residue and 721.68 mg TEAC/g residue, respectively. The hepatocyte protective effect of guava leaf extract was examined in HepG2 cells. Against tert-butyl hydroperoxide (TBHP), the viability of HepG2 cells were increased by the treatment of leaf extract. In addition, guava leaf extract led to the inhibition of reactive oxygen species (ROS) generated in HepG2 cells. The leaf extract increased the activity of glutathione (GSH), glutathione reductase (GR), and glutathione peroxidase (GPx) against oxidative stress. These results suggested that guava leaves might be regarded as a potential source natural antioxidant and a hepatoprotective material.

Guava (Psidium guajava) contain a great deal of polyphenol compound and work on the treatment of Diabetes mellitus effectively. In this study, the bioactivities of aqueous extract (GLEx) of guava leaf were investigated. Total phenolic contents of GLEx was 266.9 mg tan/g. The effects of GLEx on digestive enzymes, α-amylase, maltase and sucrase were investigated. IC50 values of GLEx against α-amylase, maltase and sucrase were 0.65 mg/ml, 2.0 mg/ml and 3.5 mg/ml respectively. The effect of GLEx on oral glucose tolerance test (OGTT) was performed in normal ICR mouse, control (dstilled water) and GLEx (aqueous extract of Guava leaf) were co-administered orally with glucose, showed reducing effect on the blood glucose level. The guava is likely to useful for prevention or improvement of hyperglycemia by lowering the blood glucose level and inhibiting glycoside hydrolase activity.

구아바 잎을 이용한 가공제품개발의 기초자료를 마련하고자 구아바 잎을 발효, 증숙 및 볶음 처리하여 품질특성을 살펴보았다. 그 결과 총 페놀성 화합물 함량의 경우 볶음 처리한 것이 높게 나타났으며, tyrosinase 저해활성 및 전자공여능은 증숙 처리한 것이 우수한 것으로 나타났다. 또한 전반적인 기호도에 있어서는 발효 및 증숙 처리한 것이 우수한 것으로 나타났다. 한편 데침 및 증숙 처리 시간에 따른 품질특성을 살펴본 결과, 총 페놀성 화합물