Citral-Containing Essential Oils as Potential Tyrosinase Inhibitors: A Bio-Guided Fractionation Approach.

Francesca Capetti,Arianna Marengo,Patrizia Rubiolo,Cecilia Cagliero,Barbara Sgorbini,Massimo Tacchini,Carlo Bicchi

doi:10.3390/plants10050969

Francesca Capetti, Arianna Marengo + Show 5 more

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https://doi.org/10.3390/plants10050969

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Abstract

Excessive melanin production causes serious dermatological conditions as well as minor aesthetic problems (i.e., freckles and solar lentigo). The downregulation of tyrosinase is a widespread approach for the treatment of such disorders, and plant extracts have often proven to be valuable sources of tyrosinase inhibitors. Citral (a mixture of neral and geranial) is an important fragrance ingredient that has shown anti-tyrosinase potential. It is highly concentrated in the essential oils (EOs) of Cymbopogon schoenanthus (L.) Spreng., Litsea cubeba (Lour.) Pers., Melissa officinalis L., and Verbena officinalis L. However, only L. cubeba EO has been investigated for use as a potential skin-whitening agent. This work evaluates the in vitro tyrosinase inhibitory activity of these EOs and studies, using bio-assay oriented fractionation, whether their differing chemical compositions influence the overall EO inhibitory activities via possible synergistic, additive, and/or competitive interactions between EOs components. The inhibitory activity of C. schoenanthus EO and that of M. officinalis EOs, with negligible (+)-citronellal amounts, were in-line with their citral content. On the other hand, L. cubeba and V. officinalis EOs inhibited tyrosinase to considerably greater extents as they contained β-myrcene, which contributed to the overall EO activities. Similar observations were made for M. officinalis EO, which bears high (+)-citronellal content which increased citral activity.

Highlights

Tyrosinase is the key enzyme in the biosynthesis of melanin pigments in several bacteria, fungi, plants, animals, and humans
This study aimed at examining the in vitro tyrosinase inhibitory activities of these essential oils (EOs) to explore whether their inhibitory activity can be ascribed to their citral content only, or whether there are other bioactive compounds that influence the inhibitory effects of the EOs
For L. cubeba, V. officinalis, and C. schoenanthus EOs, the results reported in Figure 2 correspond to the mushroom tyrosinase inhibitory activity of the EOs of 2020 because the analysis of variance revealed no statistically significant differences among EOs of different years of production (p > 0.05)

Summary

Introduction

Tyrosinase is the key enzyme in the biosynthesis of melanin pigments in several bacteria, fungi, plants, animals, and humans. Tyrosinase catalyzes the rate limiting steps in the melanin biosynthetic pathway. There are other enzymes involved in melanogenesis, only the tyrosinase-catalyzed reactions cannot occur spontaneously, whereas the remaining steps can proceed without enzyme activity at physiological pH [1]. For this reason, tyrosinase downregulation is a very widespread approach to the reduction of excessive melanin production, and the use of tyrosinase inhibitors as skin-whitening agents has demonstrated significant clinical and cosmetic prominence [2].

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