Katarzyna Gaweł-Bęben

Fruit peels might be a valuable source of active ingredients for cosmetics, leading to more sustainable usage of plant by-products. The aim of the study was to evaluate the phytochemical content and selected biological properties of hydroglycolic extracts from peels and pulps of Annona cherimola, Diospyros kaki, Cydonia oblonga, and Fortunella margarita as potential cosmetic ingredients. Peel and pulp extracts were compared for their antiradical activity (using DPPH and ABTS radical scavenging assays), skin-lightening potential (tyrosinase inhibitory assay), sun protection factor (SPF), and cytotoxicity toward human fibroblast, keratinocyte, and melanoma cell lines. The total content of polyphenols and/or flavonoids was significantly higher in peel than in pulp extracts, and the composition of particular active compounds was also markedly different. The HPLC-MS fingerprinting revealed the presence of catechin, epicatechin and rutoside in the peel of D. kaki, whereas kaempferol glucoside and procyanidin A were present only in the pulp. In A. cherimola, catechin, epicatechin and rutoside were identified only in the peel of the fruit, whereas procyanidins were traced only in the pulp extracts. Quercetin and luteolinidin were found to be characteristic compounds of F. margarita peel extract. Naringenin and hesperidin were found only in the pulp of F. margarita. The most significant compositional variety between the peel and pulp extracts was observed for C. oblonga: Peel extracts contained a higher number of active components (e.g., vicenin-2, kaempferol rutinoside, or kaempferol galactoside) than pulp extract. The radical scavenging potential of peel extracts was higher than of the pulp extracts. D. kaki and F. margarita peel and pulp extracts inhibited mushroom and murine tyrosinases at comparable levels. The C. oblonga pulp extract was a more potent mushroom tyrosinase inhibitor than the peel extract. Peel extract of A. cherimola inhibited mushroom tyrosinase but activated the murine enzyme. F. margarita pulp and peel extracts showed the highest in vitro SPF. A. cherimola, D. kaki, and F. margarita extracts were not cytotoxic for fibroblasts and keratinocytes up to a concentration of 2% (v/v) and the peel extracts were cytotoxic for A375 melanoma cells. To summarize, peel extracts from all analyzed fruit showed comparable or better cosmetic-related properties than pulp extracts and might be considered multifunctional active ingredients of skin lightening, anti-aging, and protective cosmetics.

Currently, there is an increased interest from both scientists and consumers in the application of cannabis/hemp/phytocannabinoids in skin-related disorders. However, most previous investigations assessed the pharmacological properties of hemp extracts, cannabidiol (CBD), or tetrahydrocannabinol (THC), with very few studies focusing on minor phytocannabinoids from hemp. In this context, the current work explored the in vitro anti-melanoma, anti-melanogenic, and anti-tyrosinase effects of cannabidiol (CBD) and three minor phytocannabinoids, namely cannabigerol (CBG), cannabinol (CBN), and cannabichromene (CBC). Among the tested human malignant melanoma cells (A375, SH4, and G361), only A375 cells were highly susceptible to the 48 h treatment with the four phytocannabinoids (IC50 values between 12.02 and 25.13 μg/mL). When melanogenesis was induced in murine melanoma B16F10 cells by α-melanocyte stimulating hormone (αMSH), CBD, CBG, and CBN significantly decreased the extracellular (29.76–45.14% of αMSH+ cells) and intracellular (60.59–67.87% of αMSH+ cells) melanin content at 5 μg/mL. Lastly, CBN (50–200 μg/mL) inhibited both mushroom and murine tyrosinase, whereas CBG (50–200 μg/mL) and CBC (100–200 μg/mL) down-regulated only the mushroom tyrosinase activity; in contrast, CBD was practically inactive. The current data show that tyrosinase inhibition might not be responsible for reducing the melanin biosynthesis in α-MSH-treated B16F10 cells. By evaluating for the first time the preliminary anti-melanoma, anti-melanogenic, and anti-tyrosinase properties of CBN and CBC and confirming similar effects for CBD and CBG, this study can expand the utilization of CBD and, in particular, of minor phytocannabinoids to novel cosmeceutical products for skin care.