Inhibitory effect of diphlorethohydroxycarmalol on melanogenesis and its protective effect against UV-B radiation-induced cell damage

https://doi.org/10.1016/j.fct.2010.03.001Get rights and content

Abstract

In this study, potential inhibitory effect of 21 species of marine algae on melanogenesis was assessed via tyrosinase inhibitory effect. The Ishige okamurae extract tested herein evidenced profound tyrosinase inhibitory effect, compared to that exhibited by other marine algae extracts. Thus, I. okamurae was selected for use in further experiments, and was partitioned with different organic solvents. Profound tyrosinase inhibitory effect was detected in the ethyl acetate fraction, and the active compound was identified as the carmalol derivative, diphlorethohydroxycarmalol (DPHC), which evidenced higher levels of activity than that of commercial whitening agent. Intracellular reactive oxygen species (ROS) induced by ultraviolet (UV)-B radiation was reduced by the addition of DPHC and cell viability was dose-dependently increased. Moreover, DPHC demonstrated strong protective properties against UV-B radiation via damaged DNA tail length and morphological changes in fibroblast. Hence, these results indicate that DPHC isolated from I. okamurae has potential whitening effects and prominent protective effects on UV-B radiation-induced cell damages which might be used in pharmaceutical and cosmeceutical industries.

Introduction

Ultraviolet (UV) radiation on the surface of the earth is certainly increasing as a result of the depletion of stratospheric ozone. Generally, UV radiation in solar light at low dose affects growth and metabolic activity in organism, especially photoautophic organisms, which need light for synthesis of biomass and fixation of energy. However, high-intensity or accumulated UV radiation induces overproduction of reactive oxygen species (ROS) that interact with proteins, lipids, and DNA thus altering cellular functions (He and Häder, 2002, Wang et al., 2008). This observation has stimulated research into the role of natural antioxidants that can mitigate photobiologic damage. Our interest in this field has focus on phlorotannins, a marine algal polyphenols that have been recently used in biological systems for their antioxidant activities (Ahn et al., 2007, Heo and Jeon, 2009). It now appears that important actions can be attributed to some phlorotannins, and evidence indicates that they may reduce UV radiation-mediated cutaneous disease such as epidermal hyperplasia, carcinogenesis, and melanogenesis (Pavia et al., 1997, Swanson and Druehl, 2002).

Phlorotannins are organic polymers of phloroglucinol (1,3,5-trihydroxybenzene), unique to the brown algae. They represent an interesting class of active polyphenolic compounds in the protection of UV light-induced skin damage due to their wide spectrum of activities including antioxidant, anti-diabetes, anti-HIV, and anti-allergic activities (Kakegawa et al., 1992, Heo et al., 2008, Artan et al., 2008, Heo et al., 2009). As mentioned in the previous reports with the phlorotannins, higher plants are naturally exposed to solar radiation and therefore to relatively high doses of UV radiation; thus they have developed a number of defense mechanisms against UV-induced damage, such as the capability to absorb UV radiation by accumulation of phenolic compounds in their superficial layers (Swanson and Druehl, 2002).

The objectives of the current study were to isolate diphlorethohydroxycarmalol (DPHC) from Ishige okamurae based on the results of NMR and other analytical data, and to evaluate its inhibitory effect of melanogenesis and protective effects against UV-B radiation-induced cell damage. In order to select a proper sample having higher activity, we assessed the tyrosinase inhibitory effect of 80% methanolic extracts from 21 species of marine algae; as a result, I. okamurae was selected for further experiments, owing to its higher tyrosinase inhibitory activity.

Section snippets

Materials

The marine algae were collected along the coast of Jeju Island, Korea, between October 2007 and March 2008. The samples were washed three times with tap water to remove the salt, epiphytes, and sand attached to the surface, then carefully rinsed with fresh water and maintained in a medical refrigerator at −20 °C. Thereafter, the frozen samples were lyophilized and homogenized with a grinder prior to extraction. Mushroom tyrosinase, l-tyrosine, 2′,7′-dichlorodihydrofluorescein diacetate

Tyrosinase inhibitory effect of marine algae extracts

To evaluate whether marine algae extracts possess potential inhibitory effect on melanogenesis, we investigated tyrosinase inhibitory effect of 21 species of marine algae (Table 1A). Among those marine algae extracts obtained with 80% methanol, the brown algae extracts showed relatively higher levels of tyrosinase inhibitory effect than that observed in the green and red algae extracts. It was observed that I. okamurae extract showed the highest levels of inhibitory effect (78.73%), and Ishige

Discussion

Melanogenesis is a physiological process resulting in the synthesis of melanin pigments, which play a crucial protective role against skin photo-carcinogenesis. In humans and other mammals, the biosynthesis of melanins takes place in a lineage of cells known as the melanocytes, which contain the enzyme tyrosinase (Baurin et al., 2002). Tyrosinase plays an important role in melanogenesis. Dopaquinone, an intermediate of melanogenesis, is unstable and converted to dopachrome by tyrosinase or

Conflict of interest statement

The authors declare that there are no conflicts of interest.

Acknowledgements

This research was supported by a grant from Marine Bioprocess Research Center of the Marine Bio21 Project funded by the Ministry of Land, Transport and Maritime Affairs, Republic of Korea.

References (35)

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