Kumar Dinesh, Ladaniya Milind Shivratan, Gurjar Manju, Kumar Sunil, Mendke Sachin
ICAR-Central Citrus Research Institute, Nagpur 440033, India.
Plants (Basel). 2022 Mar 24;11(7):862. doi: 10.3390/plants11070862.
Citrus fruits are grown commercially throughout the world. They are widely consumed due to their nutrients, use in energy supplements, and numerous health benefits. There is significant interest among consumers about this naturally available source, rich in flavonoids and antioxidants. However, underutilized citrus varieties remain unexplored due to the lack of information about the pool of nutritive properties they confer. Ten underutilized citrus varieties were collected from Nokrek Biosphere Reserve, West Garo Hills, Meghalaya, India, identified by UNESCO as a Biosphere reserve, to study the diversity in terms of limonin, ascorbic acid, carotenoids, browning, flavonoids, total phenol, and antioxidant activity, the contents of which varied significantly among different citrus cultivars. The results indicated that Citron and Pomelo were good sources of ascorbic acid (29.50 and 45.09 mg/100 mL), and that Khasi papeda was found to contain lower limonin content (9.21 ppm). However, in terms of flavonoids, Khasi papeda and Pomelo were found to exhibit a higher naringin content (189.13 ppm and 32.15 ppm), whereas the hesperidin content was highest in Kachai lemon, Khasi papeda, and Chinotto, at 199.51 ppm, 148.04 ppm, and 135.88 ppm, respectively. Antioxidant activity was assessed by three antioxidant assays (ABTS (radical cation azino-bis [3-ethylbenzthiazoline-6-sulfonic acid]) (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), and Ferric Reducing Antioxidant Power (FRAP)). Khasi papeda (7.48 mM L Trolox), Chinotto (7.48 mM L Trolox), and Pomelo (7.48 mM L Trolox) exhibited the highest reducing power with DPPH radical scavenging activity, and Khasi papeda (15.41 mg GAE L) possessed a higher phenolic content, whereas the antioxidant activity when assessed with ABTS and FRAP assays was highest among the underutilized species of Khasi papeda (4.84 mM L Trolox, 1.93 mM L Trolox) and Ada Jamir (4.96 mM L Trolox, 2.03 mM L Trolox), respectively. To the best of our knowledge, this is among the very few papers presenting comprehensive data on the metabolic diversity of flavonoids and antioxidant potential to characterize the underutilized citrus species. This study also demonstrated that Khasi papeda, Pomelo, Chinotto, and Kachai lemon can serve as potential sources of functional components, bioactive compounds, and antioxidants, which can be explored for further application in the processing industry for nutritional security.
柑橘类水果在全球范围内进行商业化种植。由于其营养成分、在能量补充剂中的应用以及众多健康益处，它们被广泛食用。消费者对这种富含类黄酮和抗氧化剂的天然来源非常感兴趣。然而，由于缺乏关于未充分利用的柑橘品种所具有的营养特性的信息，这些品种仍未得到充分探索。从印度梅加拉亚邦西加罗山的诺克里克生物圈保护区收集了10个未充分利用的柑橘品种，该保护区被联合国教科文组织认定为生物圈保护区，以研究柠檬苦素、抗坏血酸、类胡萝卜素、褐变、类黄酮、总酚和抗氧化活性方面的多样性，不同柑橘品种中这些成分的含量差异显著。结果表明，香橼和柚子是抗坏血酸的良好来源（分别为29.50和45.09毫克/100毫升），发现卡西酸橙的柠檬苦素含量较低（9.21 ppm）。然而，就类黄酮而言，发现卡西酸橙和柚子的柚皮苷含量较高（分别为189.13 ppm和32.15 ppm），而在卡柴柠檬、卡西酸橙和奇诺托中橙皮苷含量最高，分别为199.51 ppm、148.04 ppm和135.88 ppm。通过三种抗氧化测定法（ABTS（自由基阳离子偶氮双[３-乙基苯并噻唑啉-6-磺酸]）（ABTS）、2,2-二苯基-1-苦基肼自由基（DPPH）和铁还原抗氧化能力（FRAP））评估抗氧化活性。卡西酸橙（7.48 mM L Trolox）、奇诺托（7.48 mM L Trolox）和柚子（7.48 mM L Trolox）在DPPH自由基清除活性方面表现出最高的还原能力，卡西酸橙（15.41毫克GAE L）的酚类含量较高，而在用ABTS和FRAP测定法评估时，抗氧化活性在未充分利用的卡西酸橙品种（4.84 mM L Trolox，1.93 mM L Trolox）和阿达贾米尔（4.96 mM L Trolox，2.03 mM L Trolox）中分别最高。据我们所知，这是为数不多的几篇提供关于类黄酮代谢多样性和抗氧化潜力的综合数据以表征未充分利用的柑橘品种的论文之一。这项研究还表明，卡西酸橙、柚子、奇诺托和卡柴柠檬可作为功能成分、生物活性化合物和抗氧化剂的潜在来源，可进一步探索其在加工业中的应用，以保障营养安全。
