Traditional Small-Size Citrus from Taiwan: Essential Oils, Bioactive Compounds and Antioxidant Capacity

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.

Lime (Citrus aurantifolia (Christm.) Swingle) Essential Oils: Volatile Compounds, Antioxidant Capacity, and Hypolipidemic Effect

“…Greater consumption of vegetable and fruit has been found to be associated with lower CVD risk, for example, supplementation with tomato juice produced using a process that increases lycopene’s and dietary fiber’s effects on hyperlipidemia regulation [11,14]. Citrus fruits are a rich source of many flavonoids, especially flavanone glycosides (rutin, hesperidin, hesperetin, and quercetin) and polymethoxyflavones (nobiletin and tangeretin) which make contributions to protection against atherogenesis [1,3,15,16].…”

Protective effect of Kumquat fruits and carrot seeds extracts against brain aging in rats

“…Kumquat (In Chinese means golden orange) is one of the smallest citrus fruits (Figure 1), which is characterized by the acidic taste of flesh and soft edible peel, where the fruit can be eaten along with the peel either in the form of row fruit or as juice. It can also be used as pickles and marmalades (5). Beside the nutrients, in kumquat there are several phytochemicals in fruits including carotenoids, essential oils, ascorbic acid as well as flavonoids (6).…”

Comparative assessment of volatiles in juices and essential oils from minor Citrus fruits (Rutaceae)

“…The flavonoids found in the calamondin fruit were diosmin, hesperetin, naringin quercetin, and hesperidin. 16 The volatile fragrance of the calamondin juice was determined by headspace analysis (SPME), and monoterpenic aldehydes, alcohols, and hydrocarbons were mainly identified. 17 However, the most prominent compound in the peel oil was limonene (77.0%), while elemol (15.4%) and α-eudesmol (11.1%) represented the main components in the leaf oil.…”

“…30 The EO composition of C × myrtifolia, C mitis, and C japonica also agrees with the data from the literature for each fruit, where limonene represented the main compounds in the volatile bouquet and with the highest amount of total monoterpene hydrocarbons. 16,19,23,31…”