An excess of dihydrotestosterone (DHT) is considered to be an important factor causing acne, while testosterone 5α-reductase is responsible for converting testosterone into DHT. In the course of a search for plant resources used for treatment of acne from natural medicines, the 50% of ethanolic extract of "Eijitsu (dried fruits of
Rosa multiflora)" showed the strongest inhibitory activity against testosterone 5α-reductase in the previous screening test.
Examination of the constituents of the extract resulted in the isolation and/or identification of multiflorin A (
1), multinoside A (
2), multinoside A monoacetate (
3), isoquercitrin (
4), ursolic acid (
5), 3-acetyl ursolic acid (
6), betulinic acid (
7), 3β, 6α, 19α-trihydroxyurs-12-en-28-oic acid (
8), lauric acid (
9), myristic acid (
10), palmitic acid (
11), oleic acid (
12), linoleic acid (
13) and γ-linolenic acid (
14).
Among them, three fatty acids (
12-
14) showed inhibitory activities with IC
50 values of 52.2, 36.5 and 7.3 μg/ml, respectively. The chemical compositions of fatty acids in fractions were then examined by HPLC, as a result, the fraction with a stronger inhibitory activity showed higher contents of
12-
14. These results suggest that unsaturated fatty acids (
12-
14) could be ascribed as active principles of the 50% ethanolic extract from
R. multiflora. In addition,
5,
6,
8-
10 and
12 were isolated from
R. multiflora for the first time.
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