Quantification of Flavonoids, Phenols and Antioxidant Potential from Dropped Citrus reticulata Blanco Fruits Influenced by Drying Techniques

Abstract

Physiologically dropped immature Citrus reticulata Blanco fruits are regarded as waste and discarded in the citrus orchard but are a good source of bioactive compounds including flavonoids, antioxidants and total phenols. A study was undertaken to identify and quantify these bioactive compounds and to investigate the influence of different drying techniques, namely freeze drying and hot air oven drying, on flavonoids namely flavanone glycosides, antioxidant potential and total phenol content in immature dropped fruits of Citrus reticulata Blanco. Flavonoids were quantified in high-performance liquid chromatography (HPLC). The antioxidant activity were investigated with three assays azino-bis [3-ethylbenzthiazoline-6-sulfonic acid]) (ABTS), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), Ferric Reducing Ability of Plasma (FRAP) and total phenol content was determined. Freeze dried samples of 12 and 14 mm size retained maximum hesperidin flavonoid content (27.03% and 27.20%) as compared to the hot air dried samples (17.99%) and retained higher phenolic content ranged from 50.54–54.19 mg GAEL−1. The antioxidant activity in freeze dried fruits was from 12.21–13.55 mM L−1 Trolox and 15.27–16.72 mM L−1 Trolox with ABTS, DPPH assay and FRAP values ranging from 7.31–9.07 mM L−1 Trolox. Significant positive correlation was found between the flavonoid hesperidin with antioxidant assays and total phenolic content (TPC). The results showed that waste citrus fruits can act as potential source of bioflavonoids, especially hesperidin, and antioxidants for pharmaceutical as well as nutraceutical industry.

Impact of drying methods on natural antioxidants, phenols and flavanones of immature dropped Citrus sinensis L. Osbeck fruits

“…There are several reports 30 , 31 mentioning the higher content of hesperidin and naringin content in different cultivars of citrus (mandarin, orange, grapefruit, pummelo). The results are in agreement with study conducted by Ye et al 29 in young mandarin fruits and with Kumar et al 4 in dropped Citrus reticulata Blanco fruits. In a study with immature Citrus unshui pomace, the content of hesperidin and naringin was approximately 2.32–2.34 fold times higher in immature fruits than mature ones 32 .…”

“…2 ). The samples were stored in airtight polythene zip-lock pouches in the dark at – 20 °C till further use 4 , 13 .

Figure 2 Grinded powder of dropped fruits of Citrus sinensis L. Osbeck—( a ) After freeze drying and ( b ) After hot air oven drying.

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“…Citrus fruits are among one of the major fruit crops and play an important role in contributing to the country’s economy 1 , 2 . The genus citrus belongs to the family of Rutaceae and encompasses major group’s namely Citrus reticulata , Citrus sinensis , Citrus limon , Citrus aurantium , Citrus paradisi and Citrus grandis 3 , 4 . Citrus fruits are cultivated and cherished all over the world due to its nutritional content and characteristic flavor, taste and aroma 5 .…”

“…Citrus fruits are predominantly found to be the rich source of phytochemical like ascorbic acid, flavonoids, phenolics, antioxidants, carotenoids, etc. which plays a pivotal role in combating many diseases and development of nutraceutical and pharmaceutical drugs 3 , 4 .…”

“…The accumulation occurs during each developmental stage of fruit 12 . During normal metabolism, different reactive oxygen species (ROS) are formed which are harmful and cause damage to the human body 4 . Phenolic compounds occurring naturally in citrus fruits possess antioxidant capacity.…”