Abstract
The leaves and berries of myrtle (Myrtus communis L.) are rich in phenolic compounds, such as phenolic acids, flavonoids, and flavanols. The richness of these antioxidant compounds allows the potential use of myrtle biomasses as raw materials for medicinal and functional food products. Most of the phenolic compounds originate from the phenylpropanoid pathway, where phenylalanine ammonia lyase (PAL) enzyme activates the first step. The objective of this research is to study the activity of PAL as related to accumulation in the myrtle fruits and leaves of some phenolic compounds in the period between blossom and full berry ripening. With this aim, we compared two model genotypes with different fruit coloration. In leaves and berries of two cultivars, ‘Giovanna’ with pigmented berries and ‘Grazia’ with white berries, the PAL activity and content of polyphenols, anthocyanins, flavonoids, and tannins were determined with spectrophotometric methods. PAL activity was quite constant in leaves and variable in berries: Greater in berries of ‘Giovanna’ than in those of ‘Grazia’ cultivar, and increasing from berry color-break to full ripening. In berries, a positive correlation between PAL and flavonoids (r = 0.44), and between PAL and anthocyanins (r = 0.69), as well as a negative correlation between PAL and total polyphenols (r = −0.471), were found.
Highlights
The myrtle (Myrtus communis L.) is a medicinal and aromatic plant typical of the Mediterranean flora
Our results show that activity of the phenylalanine ammonia lyase (PAL) enzyme in myrtle berries is associated with accumulation of flavonoids and anthocyanins, suggesting that PAL is a limiting-enzyme in flavonoids biosynthesis
PAL activity seems not to be a limiting factor of phenolic compounds biosynthesis. This preliminary study on the enzymatic activity of PAL allows acquiring important knowledge on some phenolic compounds synthesis and accumulation in the myrtle plant. This is just a first step of our research program, which aimed at a complete definition of the gene expression of the PAL
Summary
The myrtle (Myrtus communis L.) is a medicinal and aromatic plant typical of the Mediterranean flora. It is a shrub, up to 5 m tall, characterized by intense green leaves rich in aromatic glands and white or pink flowers with aromatic glands, too, in the sepals. The plant use was for medical purposes, for example, in the care of cystitis and as a sedative for the stomach. Myrtle plant appreciation is in pharmacological, food, and cosmetic fields, and many studies have focused on the pharmacological properties of different parts of myrtle [3,4,5,6,7]
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