Cytotoxicity and molecular docking to DNA topoisomerase II of chalcone flavokawain B isolated from Kaempferia elegans rhizomes

Kongdech Savaspun^a,b, Siriwat Boonchaisri^b,c, Papada Chaisuriya^d, Chantragan Srisomsap^d, Jisnuson Svasti^d,e, Ruchuta Ardkhean^f, Anuchit Phanumartwiwath^g,, Pornpat Sam-ang^h,

ABSTRACT: Maceration of the air-dried rhizomes of Kaempferia elegans which were obtained from Chiang Mai, Thailand, using hexane, ethyl acetate, and methanol, was conducted. Isolation of hexane and methanol extracts yielded two known compounds: chalcone flavokawain B (1) and lactone 5,6-dehydrokawain (2), respectively. All extracts and two isolated compounds were tested for their cytotoxic activity against hepatocellular carcinoma (HepG2), acute lymphoblastic leukemia (MOLT-3), cholangiocarcinoma (HuCCA-1), and lung carcinoma (A549). Interestingly, compound 1 obtained from the crude hexane extract exhibited good cytotoxic activity against all 4 tested cancer cell lines with half maximal inhibitory concentration (IC50) values ranging from 2.84 to 6.16 ?g/ml, whereas compound 2 isolated from the crude methanol extract displayed cytotoxicity against only the MOLT-3 cell line with an IC50 value of 24.10 ?g/ml and did not show cytotoxic effect against the other cell lines. This is the first report of the anticancer activities of K. elegans in vitro. To probe plausible targets, molecular docking studies of both compounds against a potential target, the DNA topoisomerase II-alpha complex, were conducted using an anticancer drug, etoposide as a reference. The results showed that the putative binding poses of both compounds were achieved by forming pi?pi interactions with DNA residue guanidine 13, similarly to what observed in etoposide. Therefore, the bioactive compound 1 has a potential to be an important marker of this plant for medical uses.

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^a	Department of Chemistry, School of Science, University of Phayao, Phayao 56000 Thailand
^b	Traditional Lanna Medicine Research Group, School of Science, University of Phayao, Phayao 56000 Thailand
^c	Biology division, School of Science, University of Phayao, Phayao 56000 Thailand
^d	Laboratory of Biochemistry, Chulabhorn Research Institute, Bangkok 10210 Thailand
^e	Applied Biological Sciences Program, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok 10210 Thailand
^f	Princess Srisavangavadhana College of Medicine, Chulabhorn Royal Academy, Bangkok 10210 Thailand
^g	College of Public Health Sciences, Chulalongkorn University, Bangkok 10330 Thailand
^h	Department of Chemistry, Faculty of Science and Technology, Pibulsongkram Rajabhat University, Phitsanulok 65000 Thailand

* Corresponding author, E-mail: anuchit.p@chula.ac.th, pornpat.s@psru.ac.th

Received 7 Nov 2022, Accepted 26 Feb 2023

Cytotoxicity and molecular docking to DNA topoisomerase II of chalcone flavokawain B isolated from Kaempferia elegans rhizomes

Kongdech Savaspuna,b, Siriwat Boonchaisrib,c, Papada Chaisuriyad, Chantragan Srisomsapd, Jisnuson Svastid,e, Ruchuta Ardkheanf, Anuchit Phanumartwiwathg,*, Pornpat Sam-angh,*

Kongdech Savaspun^a,b, Siriwat Boonchaisri^b,c, Papada Chaisuriya^d, Chantragan Srisomsap^d, Jisnuson Svasti^d,e, Ruchuta Ardkhean^f, Anuchit Phanumartwiwath^g,, Pornpat Sam-ang^h,