Tangerines Cultivated on Madeira Island—A High Throughput Natural Source of Bioactive Compounds

Abstract

Tangerines (Citrus reticulata) are popular fruits worldwide, being rich in many bioactive metabolites. The setubalense variety cultivated on Madeira Island has an intense aroma easily distinguishable from other tangerines, being traditionally used to enrich several foods and beverages. Nonetheless, setubalense volatile composition has never been characterized, and we aimed to unveil the bioactive potential of peels and juices of setubalense tangerines and compare them with the murcott variety grown in Portugal mainland. Using headspace solid-phase microextraction coupled to gas chromatography mass spectrometry (HS-SPME/GC-MS), we identified a total of 128 volatile organic metabolites (VOMs) in the juice and peels, with d-limonene, γ-terpinene, β-myrcene, α- and β-pinene, o-cymene, and terpinolene, the most dominant in both cultivars. In contrast, setubalense juices are richer in terpenes, many of them associated with health protection. Discriminant analysis revealed a pool of VOMs, including β-caryophyllene and E-ocimene, with bioactive properties able to differentiate among tangerines according to variety and sample type (peel vs. juice). This is the first report on the volatile composition of setubalense tangerines grown on Madeira Island revealing that its pungent aroma is constituted by secondary metabolites with specific aroma notes and health properties. This is strong evidence of the higher nutraceutical value of such fruit for the human diet.

Evaluation of the Health-Promoting Properties of Selected Fruits

“…In previous works, a high concentration in different bioactive compounds, particularly phenolic compounds, has been observed in the fruits analysed in this work [ 5 , 9 , 10 , 15 , 25 ]. This observation led us to investigate the bioactive potential of the juice and peels of lemon and tangerine, pulp and seeds of pitanga, and the whole fruit of tomato and uva-da-serra.…”

“…Among them, flavonoids have been previously associated with a positive effect in the treatment of different diseases, including arthritis, diabetes mellitus, cancer and neurodegenerative disorders, as well as liver, kidney and heart diseases [ 8 ]. Overall, this protection, elicited by metabolites, presenting in citrus fruits contributes to strengthening their general awareness of functional foods [ 9 ]. For instance, lemon is very rich in a large variety of secondary metabolites, mainly monoterpenes, which are used in nutraceutical and food industries [ 10 ].…”

“…For instance, lemon is very rich in a large variety of secondary metabolites, mainly monoterpenes, which are used in nutraceutical and food industries [ 10 ]. Tangerines are another widely consumed citrus fruit that contains a similar bioactive content profile to lemon, namely in what concerns monoterpenes [ 9 ]. According to Figueira et al [ 9 , 10 ], both lemons and tangerines, grown in Madeira Island, were shown to have a very complex volatile composition with some of identified VOCs being responsible for health benefits.…”

“…Tangerines are another widely consumed citrus fruit that contains a similar bioactive content profile to lemon, namely in what concerns monoterpenes [ 9 ]. According to Figueira et al [ 9 , 10 ], both lemons and tangerines, grown in Madeira Island, were shown to have a very complex volatile composition with some of identified VOCs being responsible for health benefits. Tutunchi et al [ 11 ] and Alberca et al [ 12 ] reported the potential effects of naringenin, a flavanone with antiviral and anti-inflammatory activities, as a promising treatment strategy against COVID-19.…”

“…In this context, this study aimed to evaluate the health-promoting proprieties of fruits of regular consumption grown in Madeira Island, including the total phenolic and flavonoid contents (TPC and TFC, respectively), antioxidant capacity (ABTS and DPPH assays) and its ability to inhibit digestive enzymes linked to diabetes (α-amylase, α- and β-glucosidase) and hypertension (angiotensin-converting enzyme). The fruits were selected according to its high bioactive potential, previously reported, namely tomato (gordal variety) [ 5 , 25 ], lemon (eureka variety) [ 10 ], tangerine (setubalense variety) [ 9 ], uva-da-serra [ 15 ], and pitanga. Liquid-liquid-based ultrasound-assisted extraction (LLUSAE), an efficient extraction procedure for vegetable matrices, previously optimized in our lab [ 25 ], was used to obtain the extracts.…”