A new flavone from Malaysia Borneo Marsdenia tinctoria

Abstract Marsdenia tinctoria is an indigo producing plant commonly found in Borneo, Malaysia. In this present study, one new flavone kapitone (1) and three known compounds, that is 3,2’-dihydroxyflavone (2), 1-methylcyclobutene (3) and dimethyl isatoate (4) were isolated from the Malaysia Borneo M. tinctoria R. Br. (Apocynaceae). These compounds were isolated and characterised using extensive chromatographic and spectroscopic methods.


General experimental procedures
NMR spectra data were obtained from 600 Mhz Bruker AVANCe III (Bruker, Fallanden, Switzerland) NMR spectrometers with chemical shifts expressed in ppm and TMS as an internal standard in CdCl 3 . hReSIMS data were obtained from the Agilent 6530 Q-ToF (Agilent Technologies, Santa Clara, CA, uSA) mass-spectrometer equipped with the Agilent 1200 series Rapid Resolution lC system. The uV data were recorded using Agilent Cary 60 uV-vis Spectrophotometer (Agilent Technologies, Santa Clara, CA, uSA) using quartz cell. IR was carried out on the Perkin-elmer RX1 FTIR (Perkin-elmer, Waltham, MA, uSA) using NaCl cell.

Plant material and extraction
M. tinctoria was collected from Kapit, Sarawak, Malaysia. A voucher of the specimen is available at the herbarium of Sarawak Biodiversity Centre, Kuching, Sarawak, Malaysia (Research Permit No. SBC-RA-0089-CYM). 0.5 kg of wet whole plant was extracted with h 2 o (1 l) at 100 °C for 30 min and left for overnight in room temperature. The aqueous extract was then freeze-dried to give 2.05 g of dried solid. The dried solid was further subjected to sequential partitioning by ChCl 3 and Meoh to give ChCl 3 extract (270 mg) and Meoh extract (615 mg).

Conclusion
In this present study, we have successfully isolated and characterised a new flavone kapitone (1) which possessed the 2,3-bis(2-hydroxyphenyl)-4h-chromen-4-one structure and three known compounds, that is 3,2'-dihydroxyflavone (2), 1-methylcyclobutene (3) and dimethyl isatoate (4) from Malaysia Borneo M. tinctoria. This is the first isolation from natural product report for compounds 2 and 4 to the best of our knowledge. The compounds were not subjected to further bioassays characterisation due to the minute amount of samples isolated in this study.

Supplementary material
Supplementary material relating to this article is available online, alongside Figures S1-S17.

Disclosure statement
No potential conflict of interest was reported by the authors.