Stevia rebaudiana (Asteraceae), a perennial plant, has been used as a low-calorie sweetener and is being developed as a therapeutic agent for diabetes, hypertension, myocardial diseases, and microbial infections. Despite the common use of its leaves and stem, the bioavailability of the components present in S. rebaudiana flowers, when used as ingredients of cosmetics, has not been well investigated. Herein, we investigated the antioxidative and antimelanogenic effects of an aqueous extract of S. rebaudiana flowers (Stevia-F). Total flavonoid and phenolic content in Stevia-F were determined to be 8.64 ± 0.23 ㎎ of quercetin equivalents/100 g and 631.5 ± 2.01 ㎎ of gallic acid equivalents/100 g, respectively. The IC50 values of Stevia-F for reducing power, and 2,2-diphenyl-1-picryl-hydrazyl-hydrate radical, hydrogen peroxide, and nitric oxide scavenging activities were 5541.96, 131.39, 466.34, and 10.44 ㎍/mL, respectively. Stevia-F showed inhibitory effects on the tyrosinase (IC50 = 134.74 ㎍/mL) and α-glucosidase (IC50 = 114.81 ㎍/mL) activities. No significant cytotoxicity of Stevia-F was observed in B16F10 cells, treated with up to 100 ㎍/mL of the extract for 24 and 48 h (p > 0.05). Stevia-F (1–100 ㎍/mL) suppressed α-melanocyte stimulating hormone-induced melanin production in B16F10 cells (p < 0.05) and also inhibited the cellular tyrosinase activity (p < 0.05). Overall, our results show that Stevia-F possesses potential for inhibiting tyrosinase and α-glucosidase activities and has significant antioxidant capacity. The antimelanogenic potential of Stevia-F should extend the usage of S. rebaudiana flowers in the development of skinwhitening products.

This study was performed to determine the antimelanogenic effect and tyrosinase inhibitory activities of anthocyanin rich fraction (AN-SLP) from Liriope platyphylla Wang et Tang seeds. Anthocyanins isolated from L. platyphylla seeds revealed the presence of four major anthocyanin components, which were tentatively identified as delphinidin-3-Oglucoside, delphinidin-3-O-rutinoside, petunidin-3-O-rutinoside, and malvidin-3-O-rutinoside using semipreparative HPLC, 1H-NMR, 13C NMR, FAB-MS and LC/ES-MS. The inhibitory effect of AN-SLP on tyrosinase activity was studied using in vitro (against mushroom tyrosinase) and ex vivo (against B16 melanoma cell tyrosinase) models. Cellular tyrosinase activity was decreased by AN-SLP treatment in B 16 melanoma cells through dose dependent manner, but AN-SLP did not inhibit mushroom tyrosinase and L-DOPA oxidation directly. AN-SLP showed melanin inhibition by 53.2% at 50 μg/ml which was 0.7 times more efficient than the antimelanogenic effect of commercial arbutin and kojic acid (36.5%) also did not show cell toxicity. Additionally, AN-SLP inhibited the activity of α-glucosidase and the glycosylation of tyrosinase in melanoma cell. The resulting unsaturated glycosylation of tyrosinase makes it unstable and disturb correct transportation. From theses results, we conclude that AN-SLP could be used as anti-melanogenic agent for skin whitening.

천연물로부터 미백활성 성분의 개발을 위하여 국내 자생식물 60종으로부터 추출물을 얻어, 이들의 멜라닌 생성과정의 주된 효소인 tyrosinase 활성 억제력을 평가하였다. 평가결과 노랑하늘타리(열매), 죽황, 누리장나무(잎), 우산고로쇠(잎) 추출물이 비교적 높은 tyrosinase 활성억제효과를 보였고, 이들의 IC50 값은 50 ∼ 100 µg/mL 이었다. 이들의 멜라닌생성 억제효과를 B16F10 흑색종세포주를 이용하여 실험한 결과, 죽황추출물이 가장 높은 52 %의 멜라닌생성 저해활성을 보였으며, 이는 기존 미백제인 arbutin (42 %)에 비해 10 % 높은 것이다. 죽황추출물로부터 용매추출 및 크로마토그래피 등의 분리과정을 거쳐 10가지 미백활성 성분을 분리하였다. 이들은 모두 페놀유도체 화합물로서, SM701과 SM702, SM703, BPR211은 hydroquinone계 화합물이며, SM707은 gallic acid계, SM704와 SM705, SM706, SM708, SM709는 ferulic acid계로 확인되었다. 이들의 유리기 소거효과를 hydorquinone과 비타민 C와 비교하여 측정하였을 때. SC50 값이 SM702와 SM709의 경우 60 ∼ 70 µM로 hydroquinone과 유사하였고, SM701과 SM708은 30 ∼ 40 µM로 비타민 C (45 µM)보다 낮은 값을 보여 죽황추출물은 항산화활성이 높은 성분들을 함유하고 있음을 확인하였다. 이들 중 1,2-O-diferulylglycerol로 확인된 SM709 성분은 tyrosine hydroxylase 및 DOPA oxidase 활성을 각각 18, 60 % 억제하였고, B16F10 흑색종세포주를 이용한 멜라닌생성량 억제시험에서 62 %의 저해효과를 나타내 가장 높은 미백활성을 보였다. 따라서 죽황추출물의 미백활성은 주로 멜라닌 생성과정의 DOPA oxidsae 저해효과와 항산화효과에 의해 나타나는 것으로 생각된다.