Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Biyolojik Bilimler Bölümü, Türkiye
Tezin Onay Tarihi: 2015
Öğrenci: DENİZ İRTEM KARTAL
Danışman: NÜLÜFER TÜLÜN GÜRAY
Özet:S.absconditiflora is one of the endemic Salvia species grown in Turkey, which is consumed as a herbal tea. Because of the presence of high amounts of vesicles on their leaves, it is very rich in bioactive compounds. S.absconditiflora water and methanol extracts were studied for their antioxidant capacity by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and ABTS free radical scavenging assay. Total phenolic and total flavonoid contents were quantified by spectrophotometric methods, HPLC and LC-MS/MS analyses and the results revealed the presence of several compounds and their quantities were calculated by using 10 different standards. June water extracts showed the highest % Radical Scavenging Activity against DPPH radical. Total flavonoid content was found as one third of the total phenolic content. April methanol extracts had the highest TPC (180.77 mgGAE/ g of dried extract) and June methanol extracts had highest TFC (21.8 mg QE/ g of dried extract). Cytotoxic effects of S.absconditiflora extracts and two standards, as main phenolic components, were examined in human hepatocyte carcinoma cell line, HepG2, via XTT colorimetric and Trypan Dye Exclusion cell viability assays. IC50 values in HepG2 cell line, after 48 and 72 hour incubations were determined. Effects of S.absconditiflora water and methanol extracts on the gene expressions of several Phase I and II enzymes were further investigated. Among CYP450 enzymes, only five accounts for major drug metabolism, namely CYP3A4, CYP2D6, CYP2C9, CYP2C19, and CYP1A2 and water extracts induce the gene expression of all these CYP enzymes. Only CYP1A2, CYP2D6 and CYP2E1 gene expressions were induced with methanol extract. However, CYP2C9, CYP2C19 and CYP3A4 gene expressions were found to be inhibited with methanol extracts. CYP3A4 is the most important enzyme as its involved in almost all CYP450 mediated reactions. This inhibitory potential of S.absconditiflora methanol extract toward CYP3A4 could have potential herb-drug interaction in liver and might increase the bioavailability of co-adminestered drug and lead to toxicity. Inhibitory effect of methanol extract but not the water extract suggested that flavonoids, which exist abundantly in the methanol extract of S.absconditiflora may be responsible for this inhibition. Gene expression of all GST Mu enzyme (M1-M5) was inhibited by 3-18 fold with methanol extracts whereas water extracts inhibited M1 and M2 by 1.5 fold and induce M3 and M4 by again 1.5 fold. Both water and methanol extracts decreased the gene expression of GSTP1. According to our panel results we conclude that, the methanol extract of S.absconditiflora shows the most potent effects on CYP enzymes. On the other hand, the aqueous, water extract shows negligible effects on CYP activities. Since most individuals consume the leaves of S.absconditiflora either raw or boiled with water, the findings of this study suggest that the water extract may be safe considering the herb-drug interactions.