Phenolic Compound Content and Antioxidant Activity of Citrus Peels

Abstract

The peel from seven types of citrus was extracted with 80% methanol, and their phenolic compound content, oxygen radical absorbance capacity (ORAC), inhibitory activities of nitric oxide (NO), and reactive oxygen species (ROS) production induced by LPS and t-BHP in LPS-activated RAW 264.7 cells were measured. Total phenolic content was high in Yungkyool, Cheonhyehyang, and Jinkyool (30.6, 30.2,and 28.2 mg GAE/g, respectively), while total flavonoid content was high in Yungkyool and Jinkyool (30.3 and 25.5 mg RE/g, respectively). ORAC was the highest at 1,076 mM TE/g in Yungkyool, followed by Cheonhyehyang (1,012), Jinkyool (984), and Hallabong (914). High inhibitory activity against NO production was shown in Cheonhyehyang, Yungkyool, and Jinkyool with IC50 values of 215.3, 259.2, and 328.9 μg/mL, respectively. LPS-induced ROS production was inhibited by 16.4% and 12.8% in Hallabong and Jinkyool, while t-BHP-induced ROS production was inhibited by 28.7%, 26.1%, and 26.6% in Jinkyool, Hallabong, and Cheonhyehyang, respectively. Correlation coefficients between total phenolic, total flavonoid content, and ORAC were 0.884 and 0.855. Inhibitory activity against NO production showed higher correlation with total phenolic content than total flavonoid content. It was concluded that citrus peels had potent antioxidant activities and could be used as natural antioxidants in the food and pharmaceutical industries.

Antioxidative Properties of Machine-Drip Tea Prepared with Citrus Fruit Peels Are Affected by the Type of Fruit and Drying Method

“…Thus, the freeze-dried Cheonhyehyang (21.11 mg GAE/g) had the highest TPC, and air-dried orange DCPP had the second highest TPC. In previous studies, freeze-dried Cheonhyehyang peel had a significantly higher TPC than Hallabong and navel orange peel [ 11 , 12 ]. The TPC of freeze-dried Cheonhyehyang peel was 33 mg GAE/g [ 12 ] and 30.2 mg GAE/g [ 11 ], which was relatively higher than this study’s TPC of freeze-dried Cheonhyehyang DCPP (21.11 mg GAE/g).…”

“…In previous studies, freeze-dried Cheonhyehyang peel had a significantly higher TPC than Hallabong and navel orange peel [ 11 , 12 ]. The TPC of freeze-dried Cheonhyehyang peel was 33 mg GAE/g [ 12 ] and 30.2 mg GAE/g [ 11 ], which was relatively higher than this study’s TPC of freeze-dried Cheonhyehyang DCPP (21.11 mg GAE/g). The TPC can vary depending on the variety, harvest time, and standard substance used for the assay [ 23 ].…”

“…Citrus fruit is one of the most widely consumed fruits worldwide and contains numerous bioactive compounds such as dietary fiber, L-ascorbic acid, phenolic acid, flavonoids, limonoids, and carotenoids [ 8 , 9 ]. Moreover, the citrus peel contains higher phenolic acid and flavonoid contents, with considerably higher antioxidant activity than other parts of citrus fruit [ 10 , 11 , 12 , 13 ]. Naringin, hesperidin, nobiletin, and tangeretin are the main citrus flavonoids.…”

“…Traditionally, dried tangerine peel, referred to as ‘ Chen-pi ’, has been used as a folk medicine in Korea and China for expelling excessive phlegm with coughing, indicating the health benefits of citrus peel are well recognized. However, studies have mainly focused on the functionality and utilization of citrus peels of yuzu and tangerine [ 11 , 15 ]. There is only limited information on the peels of hybrid citrus species.…”

Antioxidative Activities of New Citrus Hybrid 'Hamilgam' Peel Extracts

“…감귤류의 항산화 활성에 대한 연구는 주로 온주밀감과 하귤 에 대한 것이 대부분이며 (Hyon et al, 2010), 그 외 재배품 종으로는 세토카, 청견, 부지화 (Hwang et al, 2013;, 제주재래종 감귤에 대한 연구로는 당유자, 사두감, 홍귤, 동정귤, 지각, 진귤, 빈귤, 인창귤 등에 관한 보고가 있 으나 (Kim et al, 2009a(Kim et al, , 2009b …”