This study evaluated the biological activity and cytoprotective effect of guava (Psidium guajava L.) branch against oxidative stress. The contents of vitamin C, beta-carotene, total carotenoids, quercetin and catechin determined were 26.783, 43.676, 65.083, 58.245, and 8.309 mg/100 g, respectively. To measure antioxidant activity, the guava branch was extracted using various concentrations of ethanol (60, 80, or 100%) and water. The highest content of polyphenols (0.245 mg gallic acid equivalent/mg residue) and flavonoids (0.128 mg cathechin equivalent/mg residue) was found in the 100% ethanol extract of the branch (E100). Moreover, E100 also possessed the highest radical scavenging activities and showed the highest inhibition rate of α-glucosidase (77.692%). E100 was the most effective extract to impart cytoprotectant activity against oxidative stress in HepG2 cells. Taken together, our results determine the promising antioxidant activity of guava branch, and indicate the potential to be applied as a natural antioxidant.

Abstract
I. 서 론
II. 연구내용 및 방법
    1. 재료 및 시약
    2. 구아바 가지 추출물 제조
    3. 비타민 C, 총 carotenoid 및 β-carotene 함량 분석
    4. Quercetin 및 catechin 함량 분석
    5. 총 폴리페놀 함량 측정
    6. 총 플라보노이드 함량 측정
    7. DPPH 라디칼 소거능 및 ABTS 라디칼 소거능 측정
    8. α-Glucosidase 저해능 측정
    9. 세포 배양
    10. 시료 독성 및 간세포 보호능 측정
    11. 통계처리
III. 결과 및 고찰
    1. 구아바 가지의 기능성 성분 함량 분석
    2. 구아바 가지 추출물의 라디칼 소거능 및 α-glucosidase 억제능 측정
    3. 산화적 스트레스에 대한 구아바 가지 추출물의 간세포 보호 효과
IV. 요약 및 결론
References

• 전아영(경성대학교 식품응용공학부) | Ahyeong Jeon (School of Food Biotechnology and Nutrition, Kyungsung University)
• 김나은(경성대학교 식품응용공학부) | Naeun Kim (School of Food Biotechnology and Nutrition, Kyungsung University)
• 천원영(경성대학교 식품응용공학부) | Wonyoung Cheon (School of Food Biotechnology and Nutrition, Kyungsung University)
• 김영화(경성대학교 식품응용공학부) | Younghwa Kim (School of Food Biotechnology and Nutrition, Kyungsung University) Corresponding author