Determination of preventive effect of Aquilaria crassna extract on 7, 12 Dimethylbenz[a]anthracene (DMBA)/UVB radiation induced skin damage in mice model.

Abstract

Repeated ultraviolet (UV) exposure, especially UVB radiation, is a risk factor for skin disorders. UVB directly destroys the cellular structure of the skin including proteins and lipids, and can damage the DNA of the skin which leads to gene mutation. As well, UVB can generate reactive oxygen species (ROS) and free radicals in skin cells. The mechanism for decreasing ROS and free radicals is called the antioxidant activity. The bioactive components of fruits, vegetables and herbal plants are extracted by that same mechanism. Herbal plants have been used for many years in traditional medicines to prevent and treat various illnesses. In Thailand, Aquilaria crassna (A. crassna), which is also called Krissana has been reported to have antioxidant activity, anti-inflammation activity and decreasing the pro-inflammatory cytokines.

The aims of this study were to determine the effects of A. crassna leaf extract (ACE) on DMBA-induced skin damage on 3-week old ICR mice, and also to determine the effects of the Mangiferin standard (MGF) on similarly induced skin damage on the ICR mice. The DMBA was applied once on the dorsal skin with repeated UVB irradiation for 16 weeks. The epidermal thickness, the expression of 4-HNE and COX-2 level were observed. The mice were divided into 5 groups, one of which was the Normal group comprising non-DMBA/non UVB irradiated mice. A second group was the Control group comprising DMBA/UVB-irradiated mice that received water). The group called Test Group 1 was DMBA/non UVB-irradiated mice receiving water, with Test Group 2 being orally administered ACE at a concentration of 250 mg/kg body weight/day and Test Group 3 was administered MGF standard at a dosage of 19.4 mg/kg body weight/day. The UVB-exposure dose was increased from 54 mJ/cm2 per exposure at week 1 to 126 mJ/cm2 at week 16 in varying weekly increments. A significant increase in epidermal skin thickness was observed in all groups, and a higher expression of 4-HNE and COX-2 showed in the Control group when compared with the Normal group, and both Test Group 1 and Test Group 3. In Test Group 2, the results showed that ACE can decrease the level of expression of 4-HNE, while the epidermal thickness and the level of expression of COX-2 were not significantly different in in this group when compared with the Control group. Further, comparing between the Control Group and Test Group 3 showed that MGF decreased the epidermal thickness in Test Group 3, and that the level of expression of 4-HNE and COX-2 in Test Group 3 differed significantly from the Control group. The comparison between the Control group and Test Group 2 showed no difference in epidermal thickness and the level of expression of COX-2. Also, it was found that both Test Group 2 and Test Group 3 showed a decrease in the level of expression of 4 HNE level. Therefore, it can be concluded that the dietary uptake of herbal plants can reduce skin damage from repeated UV exposure by decreasing epidermal thickness with an over-proliferation of keratinocytes, which is the expression of 4-HNE, while the uptake of a pure compound of MGF can decrease skin damage which showed as lower epidermal thickness, and a lower level of expression of both 4-HNE and COX-2.

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