Abstract
The effect of variation of harvest season and cultivar on the total phenolic content (TPC), total flavonoid content (TFC), HPLC-UV/DAD profile and antioxidant properties in Vaccinium ashei (Rabbiteye blueberry) leaves grown in Brazil was evaluated. The cultivars collected in December and March were Aliceblue, Powderblue, Climax, Bluegem and FloridaM. It was observed that leaves from March had the highest TPC values (222 ± 1 mg gallic acid equivalents/g to Aliceblue cultivar) and highest TFC values (49.8 ± 0.8 and 48.7 ± 0.7 µg rutin/g to Clímax and Powderblue cultivars, respectively). The chromatographic profile was quantitatively similar, however, the proportions of each compound were influenced by cultivar and harvest season. Chlorogenic acid and rutin were the main identified phenolic compounds, but chlorogenic acid was the most abundant in both harvest seasons. Antioxidant capacities values ranged from 5.80 ± 0.04 to 105 ± 2 µg/mL (DPPH) and 178 ± 5 to 431 ± 8 mmol Trolox/100 g (ORAC). The cultivar Bluegem by March had the highest values in both assays. The results indicate that the blueberry leaves from different cultivars and harvest seasons have different phenolic compounds content and different antioxidant capacities. In addition, the antioxidant properties demonstrated a high correlation with rutin content.
Highlights
Vaccinium genus, is known around the world due to its several beneficial effects for human health due to its potential activities against a wide range of degenerative diseases such as inflammatory reactions, oxidative stress induced by aging and cardiovascular problems [1,2,3,4]
Considering the variations of phenolic composition and the biological activity differences among the different cultivars, the harvest period and the limited information on the phenolic composition of rabbiteye blueberry leaves produced in Brazil, the main objectives of this study were: (1) to evaluate the total phenolic and flavonoids content of blueberry leaves of five different varieties (Clímax, Bluegem, Aliceblue, Powderblue and FloridaM) collected during two different harvest times: December and March; (2) to assess in details the metabolite profile of the phenolic compounds by HPLC-UV/DAD; (3) to determine the antioxidant properties in terms of DPPH and oxygen radicals removal ability method (ORAC); and (4) to correlate the variation of the phenolic composition and antioxidant properties with the different times of harvest and the blueberry leaves variety
The leaves collected in March presented the highest total phenolic content (TPC) and total flavonoid content (TFC) contents
Summary
Vaccinium genus (blueberry, family Ericaceae), is known around the world due to its several beneficial effects for human health due to its potential activities against a wide range of degenerative diseases such as inflammatory reactions, oxidative stress induced by aging and cardiovascular problems [1,2,3,4]. As the total phenolic compound concentration in leaves is three times higher than those observed in the fruits [9,10,11,12] there is a growing scientific interest in them. Berry phenolics comprise a wide variety of secondary metabolites divided into phenolic acids (such as hydroxybenzoic and hydroxycinnamic acids), flavonoids (flavonol, flavanol and anthocyanin) and condensed (proanthocyanidin) and hydrolysable tannins [12]. Regarding these compounds, several studies have demonstrated numerous benefits related to their high consumption, for example, to prevent oxidative damage originated by reactive oxygen species [13,14,15]. It is essential to evaluate the optimal cultivation time for the highest amount of active compounds and maximum biological activity [19]
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