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.

We investigated the quality characteristics of cookies prepared after the addition of various concentration of used guava leaf powder(0%, 1%, 3%, 5%, all w/w) as a substitute for flour. In this study, as guava leaf powder concentration rose, there was a decrease in the water content level. In addition, color, spread factor, hardness and sensory evaluation of the cookies were examined. The results showed that with an increase in guava leaf powder concentration, the L value decreased significantly, while the values for a and b of cookies increased when more guava leaf power was added to cookies. The spread factor of cookies decreased, but the hardness of cookies increased significantly, as guava leaf powder concentration increased. Cookies containing 0% and 3% of guava leaf powder showed a similar sensory evaluation score in terms of color, taste and flavor of the cookies. In the case of texture and overall consumer acceptability, cookies with 3% of guava leaf powder showed the highest score.

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.

PC12 신경세포를 이용하여 구아바 열매와 잎 추출물이 로 유도된 신경세포 독성에 대한 보호 효과를 조사하였다. 구아바 열매와 잎 열수 추출물의 총페놀성 화합물 함량은 각각 11.75 및 293.25 mg/g이었고, gallic acid 함량은 각각 22.78 및 117.34 mg/100 g이었다. 처리한 PC12 cell내의 활성산소 생성억제효과를 측정한 결과 구아바 잎열수 추출물에서 높은 활성산소 생성 억제효과를 보였다. MTT방법을 이용하

본 연구는 기능성소재 개발에 이용될 수 있는 유용한 기초자료를 얻고자 구아바 잎의 총페놀화합물의 함량, 항산화활성, tyrosinase 저해활성을 측정하였다. 1. 구이바잎 추출물의 총페놀화합물은 19.0(g/100g, D.W.)의 함량으로 강한 항산화활성을 보였다(radical 소거활성의 IC50는 102.5μg/ml, SOD 유사활성의 IC50는 49.4μg/ml).) 2. 용매분획물의 radical 소거활상을 측정한 결과, 100μg/ml의 농도에선도 ethylacetate(G-E), butanol(G-B), 물분획(G-W)은 50% 이상의 높은 소거활성을 보였다 radical 소거 활성은 G-B〉G-E〉G-W 순으로 높은 활성을 보였고, 각 분획물의 농도가 증가할수록 소거능이 높아지는 경향을 나타냈다. hexane분획(G-H)의 소거활성은 보이지 않았다. 3. 용매분획별 SOD 유사활성에 대한 결과, 100μg/ml의 농도에서 G-E, G-B, G-W는 각각 81.8, 84.7, 65.3%로 높은 활성을 나타냈으며, 각 분획물의 농도가 증가할수록 SOD 유사활성도 증가하는 경향을 나타냈다 G-H의 활성은 보이지 않았다. 4. 구아바잎의 추출물과 용매분획물의 tyrosinase저해 효과를 측정한 결과, 추출물 1mg/ml의 농도에서 60.8%의 저해효과을 보였으며, 용매분획은 G-E(65.2%), G-B(62.8%), G-W(51.6%), G-H(28.9%)의 순으로 tyrosinase 저해효과를 보였다.

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