Abstract
Background: The calamondin (Citrus microcarpa Bunge) and the kumquat (Fortunella crassifolia Swingle) are two small-size citrus fruits that have traditionally been consumed in Taiwan; however, there has been a lack of scientific research regarding the active compounds and functionalities of these fruits. Methods: Analysis of volatile composition of essential oil and phytosterol was carried out using Gas Chromatography–Mass Spectrometry (GC-MS). Flavonoid and limonoid were analyzed by High Performance Liquid Chromatography (HPLC). Moreover, antioxidant capacity from their essential oils and extracts were assessed in vitro. Results: The compositions of the essential oils of both fruits were identified, with the results showing that the calamondin and kumquat contain identified 43 and 44 volatile compounds, respectively. In addition, oxygenated compounds of volatiles accounted for 4.25% and 2.04%, respectively, consistent with the fact that oxygenated compounds are generally found in high content in citrus fruits. In terms of flavonoids, the calamondin exhibited higher content than the kumquat, with disomin-based flavonoids being predominant; on the other hand, phytosterol content of kumquat was higher than that of calamondin, with amyrin being the dominant phytosterol. Both of them contain high amounts of limonoids. The ethanol extracts and essential oils of small-sized citrus fruits have been shown to have antioxidant effects, with those effects being closely related to the flavonoid content of the fruit in question. Conclusions: The present study also reviewed antioxidant activity in terms of specific bioactive compounds in order to find the underlying biological activity of both fruits. The calamondin and kumquat have antioxidant effects, which are in turn very important for the prevention of chronic diseases.
Highlights
Citrus fruits constitute a great proportion of fruit tree crops grown throughout the world, with fresh citrus fruits being exported or sold in local markets, and used for processing
Essential oils are produced by cells within the rind of a citrus fruit
The results showed that with regard to the antioxidants in the calamondin and kumquat samples, the total phenolic contents were 5.77 and 2.29 GAE mg/g, respectively, and the total flavonoid contents were 2.71 and 1.36 QE mg/g, respectively
Summary
Citrus fruits constitute a great proportion of fruit tree crops grown throughout the world, with fresh citrus fruits being exported or sold in local markets, and used for processing. The possible beneficial effects of citrus fruits are due to the micronutrients (included ascorbic acid, dietary fiber, potassium and folate), functional ingredients, antioxidant nutraceuticals, and acid, dietary fiber, potassium and folate), functional ingredients, antioxidant nutraceuticals, and phytochemical substances that they contain [9]. These components of the fruits, especially when phytochemical substances that they contain [9]. Peel oils and pectins are important of such products are lower than those of whole citrus fruits [11,12].
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