No abstract

Thioxanthone derivatives were docked, synthesized, and tested for their anticancer activity. The molecular docking results showed that 1-hydroxythioxanthone, 2-chloro-1-hydroxythioxanthone, and 4-chloro-1-hydroxythioxanthone gave lower binding energy than erlotinib demonstrating that those thioxanthones have stronger interaction in the active site of EGFR protein. The addition of one hydroxyl and chloro groups on 1-hydroxythioxanthone greatly enhanced its inhibition in EGFR protein. All thioxanthone derivatives had hydrogen bonding interaction with MET769 residue. The in vitro anti-cancer assay against all cancer cells (T47D, HeLa, WiDr, A549) revealed that 2-chloro-1-hydroxythioxanthone and 4-chloro-1hydroxythioxanthone gave lower IC 50 than 1-hydroxythioxanthone due to the addition of one chloro substituent. Meanwhile, 1,3-dihydroxythioxanthone exhibited the strongest anticancer activity, as well as the highest selectivity index (3.22-19.55) among the other thioxanthones. Based on these findings, 1,3-dihydroxythioxanthone is a potential anticancer drug candidate for further development in the future.

A new series of xanthyl-cinnamate hybrid compounds (4a-d) have been synthesized and screened through in vitro assay against four human cancer cell lines, i.e., HeLa, T47D, A549, and WiDr. The results revealed that xanthone hybridization with cinnamic acid increases the selectivity of the compounds with SI values of 2.75–209.03 compared to its parent oxygenated-xanthone. Compound 1,3-dihydroxyxanthen-6-yl cinnamate (4c) showed high cytotoxic activity against WiDr cell lines with an IC50 value of 39.57 µM. Molecular docking studies revealed the possible binding modes of all hybrid compounds with EGFR protein. A complex of 3,6-dihydroxyxanthen-1-yl cinnamate (4d)-EGFR, as the best binding model, exhibited higher predicted EGFR inhibitory activity than erlotinib and oxygenated-xanthone with a ΔG and Ki value of -35.02 kJ/mol and 0.74 µM, respectively. Compounds 4c and 4d were chosen as the most potent derivates from the study.

Plasmodium falciparum (P. falciparum) is the most fatal among the other Plasmodium parasites that infect humans with the malaria disease. Currently, the resistance of P. falciparum against some antifolate drugs has become a severe problem. On the other hand, xanthone and thioxanthone derivatives have been reported to have remarkable antimalarial activity. However, molecular docking studies have not evaluated thioxanthone derivative compounds as antimalarial agents. Accordingly, this research investigated the binding pose and inhibition mechanism of several thioxanthone derivatives against P. falciparum proteins DHFR (PDB ID: 1J3K) and DHODH (PDB ID: 1TV5) through molecular docking study. The compound structures were geometrically optimized using Gaussian 09 software and docked to the receptors using AutoDock4 software. The results showed that the free binding energy of thioxanthone derivatives ranged between -6.77 to -7.50 and -8.45 to -9.55 kcal mol–1 against pfDHFR and pfDHODH, respectively, with RMSD values of less than 2 Å. Compound F (4-iodo-3,4-dihydroxy-thioxanthone) gave the most substantial free binding energy against both proteins. Furthermore, the hydrogen bond interaction of compound F was the same as the native ligands of pfDHFR and pfDHODH. These results suggested that compound F has a more robust interaction in pfDHFR and pfDHODH. Thus, it is promising to further evaluate the compound as a candidate for a new antimalarial agent.