In the present work, three hydroxyxanthones were synthesized in 11.15–33.42% yield from 2,6-dihydroxybenzoic acid as the starting material. The chemical structures of prepared hydroxyxanthones have been elucidated by using spectroscopic techniques. Afterward, the hydroxyxanthones were evaluated as antioxidant agents through radical scavenging assay; and anticancer agents through in vitro assays against WiDr, MCF-7, and HeLa cancer cell lines. Hydroxyxanthone 3b was categorized as a strong antioxidant agent (IC50 = 349 ± 68 µM), while the other compounds were categorized as moderate antioxidant agents (IC50 > 500 µM). On the other hand, hydroxyxanthone 3a exhibited the highest anticancer activity (IC50 = 184 ± 15 µM) and the highest selectivity (SI = 18.42) against MCF-7 cancer cells. From the molecular docking study, it was found that hydroxyxanthone 3a interacted with the active sites of Topoisomerase II protein through Hydrogen bonding with DG13 and π–π stacking interactions with DA12 and DC8. These findings revealed that hydroxyxanthones are potential candidates to be developed as antioxidant and anticancer agents in the future.
Indonesia is rich with essential oils such as anise and clove leave oils. In respect to explore the potential utilization of these resources, it has been conducted the transformation of p-hydroxybenzaldehyde and vanillin (4-hydroxy-3-methoxy benzaldehyde) respectively derived from anise oil and clove leaves oil to a series of Carylcalix [4]resorcinarenes and C-arylcalix[4]pyrogallolarene macrocycles. Treatment of these aldehydes with resorcinol in the presence of HCl in absolute ethanol at reflux for 8 h afforded C-4-hydroxyphenylcalix[4]resorcinarene (3a) and C-4-hydroxy-3-methoxy phenyl-calix[4]resorcinarene (3b) in good yields. When the aldehydes were treated with pyrogallol under the similar condition, the products were C-4-hydroxyphenyl calix[4]pyrogallolarene (3c) and C-4-hydroxy-3-methoxyphenylcalix[4]pyrogallolarene (3d) which were also obtained in excellent yields. Treatment of these calix[4]resorcinarenes and calix[4]pyrogallolarenes with cinnamoyl chloride and benzoyl chloride in pyridine afforded the corresponding cinnamate esters and benzoate esters in high yields. The resulted C -arylcalix-[4]resorcinarenes and C-arylcalix[4]pyrogallol arenes were subjected to antioxidant activity test using DPPH method and showed strong activity with IC50 values of 15-80 μg/mL. In terms of the synthesized calix cinnamates, the compounds showed UV-B absorption with SPF values of 15-30 at a concentration of 25 ppm which demonstrate their potential to be applied as a UV-B protector. Furthermore, these compounds were also tested for their photostability on the UV-B region and the results showed that the compounds were still unstable under irradiation for 30 min.
The previous study showed that xanthone had antiplasmodial activity. Xanthone, with additional hydroxyl groups, was synthesized to increase its antiplasmodial activity. One of the strategies to evaluate a compound that can be developed into an antimalarial drug is by testing its mechanism in inhibiting heme polymerization. In acidic condition, hematin can be polymerized to β-hematin in vitro, which is analog with hemozoin in Plasmodium. This study was conducted to evaluate the antiplasmodial activity of hydroxyxanthone derivative compounds on two strains of Plasmodium falciparum 3D-7 and FCR-3, to assess inhibition of heme polymerization activity and determine the selectivity of hydroxyxanthone derivative compounds. The antiplasmodial activity of each compound was tested on Plasmodium falciparum 3D-7 and FCR-3 with 72 hours incubation period, triplicated in three replications with the microscopic method. The compound that showed the best antiplasmodial activity underwent flow cytometry assay. Heme polymerization inhibition test was performed using the in vitro heme polymerization inhibition activity (HPIA) assay. The antiplasmodial activity and heme polymerization inhibition activity were expressed as the 50% inhibitory concentration (IC50). In vitro cytotoxicity was tested using the MTT assay method on Vero cell lines to determine its selectivity index. The results showed that among 5-hydroxyxanthone derivative compounds, the 1,6,8-trihydroxyxanthone had the best in vitro antiplasmodial activity on both 3D-7 and FCR-3 Plasmodium falciparum strains with IC50 values of 6.10 ± 2.01 and 6.76 ± 2.38 μM, respectively. The 1,6,8-trihydroxyxanthone showed inhibition activity of heme polymerization with IC50 value of 2.854 mM and showed the high selectivity with selectivity index of 502.2–556.54. In conclusion, among 5-hydroxyxanthone derivatives tested, the 1,6,8-trihydroxyxantone showed the best antiplasmodial activity and has heme polymerization inhibition activity and high selectivity.
Nowadays, cancer is one of the most fatal diseases in developed and developing countries. Therefore, it is an urgent need to find more effective anticancer drugs among the recent commercially available standard drugs. Xanthone derivatives have been researched as anticancer drugs due to their ease of synthesis and structure modification, as well as their excellent anticancer activity. In this work, the in vitro anticancer activity of hydroxyxanthones against the human liver carcinoma cell line (HepG2) was evaluated. Among the twenty-two hydroxyxanthones, 1,3,6,8-tetrahydroxyxanthone was found as the most active anticancer agent with an IC50 value of 9.18 μM, which was better than doxorubicin as the standard drug. From the molecular docking studies against topoisomeraseIIα and two c-KIT protein kinases, 1,3,6,8-tetrahydroxyxanthone yielded strong binding energy in a range of -25.48 to -30.42 kJ/mol. The 1,3,6,8-tetrahydroxyxanthone could bind on the active site of these protein receptors through hydrogen bonds with key amino acid residues (Glu640, Cys673, Gln767, Met769, Asp810, and Asp831), as well as nitrogen bases (Adenine12 and Guanine13), thus leading to the death of HepG2 cancer cells through the apoptosis mechanism.
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