The myrtle (Myrtus communis L.) is a spontaneous aromatic shrub, belonging to the Myrtaceae family. Since ancient times, the plant has been used for medical purposes. Due to the high quantity of essential oils in the vegetative organs, the myrtle is used in pharmaceutical, cosmetic, and food fields. Numerous studies show the high antioxidant activity of myrtle berries and leaves and its derived products. Phenolic compounds, as flavonoids and tannins, are the main responsible of this property. Most phenols compounds originate from the phenylalanine produced by the biosynthetic pathway of shikimic acid. The enzyme phenylalanine ammonia lyase (PAL) catalyzes condensation of a molecule of L-phenylalanine and four molecules of coenzyme-A with the formation of a trans-cinnamic acid and ammonium ion. The conversion of trans-cinnamic acid into flavonoids, such as anthocyanins, requires other reactions catalyzed by specific enzymes. In several fruit species, the accumulation of anthocyanins and other flavonoids correlated with PAL activity, through the support of cinnamic acid. The aim of this work was to study the activity of PAL in berry and leaves as related to the changes in the amounts of total polyphenols, anthocyanins, flavonoids, and tannins from flowering to berry maturation in two model cultivars of myrtle selected in Sardinia: One with pigmented berries and one with unpigmented berries. PAL activity was quite constant in leaves and variable in berries, greater in berries of pigmented cultivar “Giovanna” 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. Our results show that activity of the PAL enzyme in myrtle berries is associated with accumulation of flavonoids and anthocyanins, suggesting that PAL is a limiting-enzyme in flavonoids biosynthesis.
PAL enzymatic activity (phenylalanine ammonium lyase) in pigmented and white myrtle (Myrtus communis L.) cultivars / Medda, Silvia; Dessena, Leonarda; Mulas, Maurizio. - (2021), pp. 131-132. (Intervento presentato al convegno II CONVEGNO AISSA #UNDER40. tenutosi a Sassari nel 1-2 luglio 2021).
PAL enzymatic activity (phenylalanine ammonium lyase) in pigmented and white myrtle (Myrtus communis L.) cultivars
Silvia MeddaMembro del Collaboration Group
;Leonarda DessenaMembro del Collaboration Group
;Maurizio Mulas
Membro del Collaboration Group
2021-01-01
Abstract
The myrtle (Myrtus communis L.) is a spontaneous aromatic shrub, belonging to the Myrtaceae family. Since ancient times, the plant has been used for medical purposes. Due to the high quantity of essential oils in the vegetative organs, the myrtle is used in pharmaceutical, cosmetic, and food fields. Numerous studies show the high antioxidant activity of myrtle berries and leaves and its derived products. Phenolic compounds, as flavonoids and tannins, are the main responsible of this property. Most phenols compounds originate from the phenylalanine produced by the biosynthetic pathway of shikimic acid. The enzyme phenylalanine ammonia lyase (PAL) catalyzes condensation of a molecule of L-phenylalanine and four molecules of coenzyme-A with the formation of a trans-cinnamic acid and ammonium ion. The conversion of trans-cinnamic acid into flavonoids, such as anthocyanins, requires other reactions catalyzed by specific enzymes. In several fruit species, the accumulation of anthocyanins and other flavonoids correlated with PAL activity, through the support of cinnamic acid. The aim of this work was to study the activity of PAL in berry and leaves as related to the changes in the amounts of total polyphenols, anthocyanins, flavonoids, and tannins from flowering to berry maturation in two model cultivars of myrtle selected in Sardinia: One with pigmented berries and one with unpigmented berries. PAL activity was quite constant in leaves and variable in berries, greater in berries of pigmented cultivar “Giovanna” 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. Our results show that activity of the PAL enzyme in myrtle berries is associated with accumulation of flavonoids and anthocyanins, suggesting that PAL is a limiting-enzyme in flavonoids biosynthesis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
