• Applied Biological Chemistry
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• v.40 no.6
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• pp.501-507
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• 1997

Chloroplasts isolated from Stevia rebaudiana Bertoni leaves contained an enzyme activity which catalyzed hydroxylation of ent-kaurenoic acid (ent-kaur-16-en-19-oic acid; ent-KA) to steviol (ent-13-hydroxy kaur-16-en-19-oic acid), the diterpenoid carboxylic alcohol which is the aglycone of sweet stevioside-related glycosides. $[^(14)C]-methylated$ ent-KA was used to localize ent-KA hydroxylase. $[^(14)C]-methyl-KA$ was most actively was transformed into methyl-steviol in chloroplast. The enzymatic activity was found in stroma fraction but not in thylakoid membrane in Stevia rebaudiana Bertoni. However, ent-KA 13-hydroxylase activity was not detected in stroma fraction of either Spinacia oleracea and Solidago altissima. The reaction products using $[^(14)C]-methyl-KA$ were purified and identified on TLC autoradiogram. The hydroxylation of ent-KA from stromal protein to form steviol required NADPH and oxygen. FAD and riboflavin stimulated the enzyme activity 1.5-and 1.7-fold, respectively. It also turned out that the activity of this enzyme using methyl-KA as a substrate was 16.7% that of ent-KA. The purified ent-KA 13-hydroxylase did not act on t-cinnamic acid, 4-hydroxyphenyl acetic acid, choline and resorcinol, known as monooxygenase and hydroxylase substrates.

• Natural Product Sciences
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• v.15 no.1
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• pp.50-54
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• 2009

A simple and reliable reversed phase HPLC method was developed to determine pharmacologically active compounds ent-continentalic acid, kaurenoic acid, and continentalic acid from the roots of Aralia cordata. Quantitative analysis of diterpenoids of A. cordata were performed by reverse phase C-18 column using a isocratic of acetonitrile : 0.1% trifluoroacetic acid(70:30) with UV detection at 205 nm. The correlation coefficients of each calibration curve of ent-continentalic acid, kaurenoic acid, and continentalic acid were 0.9987, 0.9983, and 0.9986, respectively. The detection limit of ent-continentalic acid, kaurenoic acid, and continentalic acid were $0.5{\sim}1.0\;{\mu}g/mL$, respectively. The contents of ent-continentalic acid (1), kaurenoic acid (2), and continentalic acid (3) of the roots of A. cordata collected from seventeen district markets in Korea were $0.09{\sim}0.75\;mg/g$, $1.09{\sim}5.43\;mg/g$, and $2.69{\sim}9.08\;mg/g$, respectively.

• Journal of Life Science
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• v.34 no.4
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• pp.215-226
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• 2024

Aralia continentalis is widely distributed in Far East Asian countries such as Korea, China, and Japan. A. continentalis has traditionally been used as an herbal remedy for various conditions, including analgesia, headache, inflammation, lameness, lumbago, rheumatism, and dental diseases in Korea. Previously, epi-continentalic acid, continentalic acid, and kaurenoic acid as major active biological compounds belonging to the diterpenoid class were identified. To synthesize diterpenoid derivatives with enhanced bioavailability, Fusarium fujikuroi was employed to biotransform diterpenoids due to its known antibacterial activity. This yielded two derivatives of kaurenoic acid, namely 16α-hydroxyent-kauran-2-on-19-oic acid and 2β, 16α-dihydroxy-ent-kauran-19-oic acid, with their chemical structures elucidated via NMR analysis. These derivatives exhibited increased polarity compared to kaur- enoic acid, as evidenced by their retention time on preparative HPLC using the ODS-A column and structural modifications. Evaluation of their antidiabetic activity targeting PTP1B, a negative regulator of the insulin signaling pathway, revealed inhibitory activities of 30.8% and 27.6%, respectively, at a concentration of 4 ㎍/ml. Additionally, both derivatives demonstrated low cytotoxicity, with an IC50 value 18 times higher than kaurenoic acid. Therefore, the augmented water solubility and reduced toxicity of 16α-hydroxy-ent-kauran-2-on-19-oic acid and 2β, 16α-dihydroxy-ent-kauran-19-oic acid, resulting from biotransformation by F. fujikuroi, render them promising candidates for industrial applications.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.4
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• pp.289-295
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• 2017

A. koreanum was investigated to identify the constituents possessing whitening effects. As anti-melanogenesis activities were screened for the ethanol extract and solvent fractions, n-hexane (Hex) and ethyl acetate (EtOAc) fractions showed the most potent activities. Three constituents were isolated from the n-Hex fraction of A. koreanum; kaurenoic acid (1), $16{\alpha}$-hydro-17-isovaleroyloxy-ent-kauran-19-oicacid (2), $16{\alpha}$-hydroxy-17-isovaleroyl-oxy-ent-kauran-19-oic acid (3). The chemical structures of the isolated compounds were elucidated based on the spectroscopic data including $^1H$ and $^{13}C$ NMR spectra, as well as comparison of the data to the literature values. Whitening effects were studied for the isolated compounds. Upon the anti-melanogenesis test using ${\alpha}-MSH$ stimulated B16F10 melanoma cells, the compounds 1, 2 and 3 inhibited the cellular melanogenesis and intracellular tyrosinase activities effectively. Based on these results, A. koreanum stems extract could be potentially applicable as whitening ingredients in cosmetic formulations.