Tyrosinase is a multifunctional, glycosylated, and copper-containing oxidase, which catalyzes the first two steps in mammalian melanogenesis and is responsible for enzymatic browning reactions in damaged fruits during post-harvest handling and processing. Neither hyperpigmentation in human skin nor enzymatic browning in fruits are desirable. These phenomena have encouraged researchers to seek new potent tyrosinase inhibitors for use in foods and cosmetics. This article surveys tyrosinase inhibitors newly discovered from natural and synthetic sources. The inhibitory strength is compared with that of a standard inhibitor, kojic acid, and their inhibitory mechanisms are discussed.

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An Updated Review of Tyrosinase Inhibitors

Phenolic compounds constitute a group of secondary metabolites which have important functions in plants. Besides the beneficial effects on the plant host, phenolic metabolites (polyphenols) exhibit a series of biological properties that influence the human in a health-promoting manner. Evidence suggests that people can benefit from plant phenolics obtained either by the diet or through skin application, because they can alleviate symptoms and inhibit the development of various skin disorders. Due to their natural origin and low toxicity, phenolic compounds are a promising tool in eliminating the causes and effects of skin aging, skin diseases, and skin damage, including wounds and burns. Polyphenols also act protectively and help prevent or attenuate the progression of certain skin disorders, both embarrassing minor problems (e.g., wrinkles, acne) or serious, potentially life-threatening diseases such as cancer. This paper reviews the latest reports on the potential therapy of skin disorders through treatment with phenolic compounds, considering mostly a single specific compound or a combination of compounds in a plant extract.

The Potential of Plant Phenolics in Prevention and Therapy of Skin Disorders

The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

Artocarpus: A review of its traditional uses, phytochemistry and pharmacology

Tyrosinase (EC 1.14.18.1), a copper-containing enzyme, can cause enzymatic browning in raw fruits, vegetables, and beverages. Browning is an undesirable reaction that is responsible for less attractive appearance and loss in nutritional quality. These phenomena have encouraged researchers to seek new potent tyrosinase inhibitors for use in the food industry. This article reviews recent studies on tyrosinase inhibitors of natural and synthetic origins. The information offered here should help food industry in developing and using potential tyrosinase inhibitors desirable efficacy and safety, and for improving food quality.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1541-4337.2012.00191.x

Natural and Synthetic Tyrosinase Inhibitors as Antibrowning Agents: An Update

In our previous efforts to find new tyrosinase inhibitory materials, we investigated 44 Indonesian medicinal plants belonging to 24 families. Among those plants, the extract of Artocarpus heterophyllus was one of the strongest inhibitors of tyrosinase activity. By activity-guided fractionation of A. heterophyllus wood extract, we isolated artocarpanone, which inhibited both mushroom tyrosinase activity and melanin production in B16 melanoma cells. This compound is a strong candidate as a remedy for hyperpigmentation in human skin.

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Inhibitory Effect of Artocarpanone from Artocarpus heterophyllus on Melanin Biosynthesis

Biological activity and phytochemical analysis of three Indonesian medicinal plants, Murraya koenigii, Syzygium polyanthum and Zingiber purpurea.

Objective
To screen crude extracts of propolis, bee pollen and honey from four stingless bee species [Trigona incisa (T. incisa)], Timia apicalis, Trigona fusco-balteata and Trigona fuscibasis) native to East Kalimantan, Indonesia for cytotoxic activity against five human cancer cell lines (HepG2, SW620, ChaGo-I, KATO-III and BT474).

In vitro cytotoxicity of Indonesian stingless bee products against human cancer cell lines

Isoprenoid-substituted flavonoids from wood of Artocarpus heterophyllus on B16 melanoma cells: cytotoxicity and structural criteria.

Purpose: To evaluate the anti-cancer properties of the diethylether extract of Sukun (Artocarpus altilis) wood. Methods: The extract was tested in human T47D breast cancer cells and examined for its effect on cell viability, nuclear morphology and sub-G1 formation. Cell viability was determined by microculture tetrazolium technique (MTT), nuclear morphology investigated using 4’-6-diamidino-2-phenylindole (DAPI) staining technique, and cell cycle progression monitored by sub-G1 apoptosis assay using flow cytometry. Results: The results showed decreasing cell viability in a concentration-dependent manner. Altered cell morphology after treatment with the extract demonstrated that cells experienced apoptosis. Cell cycle analysis indicated that the number of cells in sub-G1 phase rose with increasing concentrations of the extract. Conclusion: The data demonstrate that Sukun wood extract induced apoptosis and sub-G1 phase formation in breast cancer (T47D) cells, and therefore, has a potential as an anti-cancer agent.

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Enos Tangke Arung

Papers

Inhibitory Effect of Artocarpanone from Artocarpus heterophyllus on Melanin Biosynthesis

Biological activity and phytochemical analysis of three Indonesian medicinal plants, Murraya koenigii, Syzygium polyanthum and Zingiber purpurea.

In vitro cytotoxicity of Indonesian stingless bee products against human cancer cell lines

Isoprenoid-substituted flavonoids from wood of Artocarpus heterophyllus on B16 melanoma cells: cytotoxicity and structural criteria.

Anti-Cancer Properties of Diethylether Extract of Wood from Sukun (Artocarpus altilis) in Human Breast Cancer (T47D) Cells