Insight into Composition of Bioactive Phenolic Compounds in Leaves and Flowers of Green and Purple Basil

Abstract

Basil (Ocimum basilicum L.) is a culinary, medicinal, and ornamental plant appreciated for its antioxidant properties, mainly attributed to high content of rosmarinic acid. This species also includes purple varieties, characterized by the accumulation of anthocyanins in leaves and flowers. In this work, we compared the main morphological characteristics, the antioxidant capacity and the chemical composition in leaves, flowers, and corollas of green (‘Italiano Classico’) and purple (‘Red Rubin’ and ‘Dark Opal’) basil varieties. The LC-ESI-MS/MS analysis of individual compounds allowed quantifying 17 (poly)phenolic acids and 18 flavonoids, differently accumulated in leaves and flowers of the three varieties. The study revealed that in addition to rosmarinic acid, basil contains several members of the salvianolic acid family, only scarcely descripted in this species, as well as, especially in flowers, simple phenolic acids, such as 4-hydroxybenzoic acid and salvianic acid A. Moreover, the study revealed that purple leaves mainly contain highly acylated anthocyanins, while purple flowers accumulate anthocyanins with low degree of decoration. Overall, this study provides new biochemical information about the presence of not yet characterized bioactive compounds in basil that could contribute to boosting the use of this crop and to gaining new knowledge about the roles of these compounds in plant physiology.

Nitrogen Starvation and Nitrate or Ammonium Availability Differently Affect Phenolic Composition in Green and Purple Basil

“…Moreover, our study confirms, in plants grown in hydroponic condition, that leaves of purple basil possess higher PAL activity than those of green basil (Table 2), consistent with what reported for in vitro cultured basil seedlings [31], and, by means of RNA-Sequencing analysis, for potted plants grown outdoors [45], suggesting that purple cultivars are able to maintain this trait in a broad range of growth conditions. Furthermore, the results about (poly)phenolic acids and flavonoids (Figure 3; Figure 4, Supplementary Table S2) are highly consistent with our recent description of the composition of bioactive molecules in IC and RR leaves [5]. The present work confirms that basil leaves contain, in addition to high levels of rosmarinic and chicoric acids, small amounts of salvianolic acids L and K. Considering the pharmacological properties of salvianolic acids [48], the presence of these compounds could contribute to enhance the nutraceutical value of basil.…”

“…In particular, the leaf antioxidant capacity was very similar in IC and RR plants, but RR leaves showed higher levels of total phenols, most likely due to anthocyanin accumulation. Hence, in basil leaves, the antioxidant capacity appears to be very poorly correlated to the contents of total phenols and anthocyanins, as reported by several authors [5,46,47]. Moreover, our study confirms, in plants grown in hydroponic condition, that leaves of purple basil possess higher PAL activity than those of green basil (Table 2), consistent with what reported for in vitro cultured basil seedlings [31], and, by means of RNA-Sequencing analysis, for potted plants grown outdoors [45], suggesting that purple cultivars are able to maintain this trait in a broad range of growth conditions.…”

“…The contents of total phenols and antioxidant capacity in leaves were evaluated as previously described [5], with some modifications. Briefly, samples were homogenized in 1.5 volumes (v/w) of methanol and centrifuged at 10,000× g for 30 min.…”

“…Briefly, phenolic compounds were purified by extraction in CHCl 3 :CH 3 OH:H 2 O (12:5:1 v/v/v, pH 2 by addition of FA) and purification by phase partitioning, according to Tattini et al [41]. Samples were then filtered by Millex HV (0.45 µm, Merck Life Science, Milan, Italy), diluted, and analyzed by LC-ESI-MS/MS (Liquid Chromatography -ElectroSpray Ionization -tandem mass spectrometry) as previously described [5]. Briefly, samples were analyzed by HPLC (1200 series; Agilent Technologies Italia, Cernusco sul Naviglio, Italy) coupled with ESI-Q-TOF (ESI-Quadrupole-Time Of Flight mass spectrometer, 6520, Agilent Technologies) on a XDB-C18 column…”

“…Overall, basil contains a complex mixture of flavonoids and (poly)phenolic acids with antioxidant properties, among which rosmarinic and chicoric acids are the most abundant [3][4][5]. These compounds contribute to the technological quality of basil [3], and to some of the beneficial properties of leaf extracts, such as the cardioprotective and hypoglycemic activities [6].…”