Root decoctions of anthraquinone-containing plants are often taken as postpartum tonic and aphrodisiac. Anthraquinones are known for their diverse biological activities, especially antioxidant and anticancer. A series of 35 anthraquinones was generated by isolation from Rubiaceae plants and synthesis. Their UV/vis spectrum depends on the nature and relative positions of auxochromic substituents on the basic skeleton. To predict the maximum absorption bands for the current series of anthraquinones, excited sate calculations were performed using TD-DFT, CIS, ZINDO methods. The results showed that the use of PBE0 or its combination with B3LYP and B3P86 hybrid functionals are the most suitable to reproduce accurately the experimental λMAX. The structure–property relationships (SPRs) were established based on structural and electronic properties of the anthraquinones and showed (i) the importance of the number and position of OH groups and (ii) the positive contribution of the electrophilicity and hardness as electronic descriptors on position and amplitude of the maximum absorption bands.

Investigations on the cytotoxic effects of the crude methanol and fractionated extracts (hexane, ethyl acetate) C. mangga against six human cancer cell lines, namely the hormone-dependent breast cell line (MCF-7), nasopharyngeal epidermoid cell line (KB), lung cell line (A549), cervical cell line (Ca Ski), colon cell lines (HCT 116 and HT-29), and one non-cancer human fibroblast cell line (MRC-5) were conducted using an in-vitro neutral red cytotoxicity assay. The crude methanol and fractionated extracts (hexane and ethyl acetate) displayed good cytotoxic effects against MCF-7, KB, A549, Ca Ski and HT-29 cell lines, but exerted no damage on the MRC-5 line. Chemical investigation from the hexane and ethyl acetate fractions resulted in the isolation of seven pure compounds, namely (E)-labda-8(17),12-dien-15,16-dial (1), (E)-15,16-bisnor-labda-8(17),11-dien-13-on (2), zerumin A (3), β-sitosterol, curcumin, demethoxycurcumin and bis-demethoxycurcumin. Compounds 1 and 3 exhibited high cytotoxic effects against all six selected cancer cell lines, while compounds 2 showed no anti-proliferative activity on the tested cell lines. Compound 1 also demonstrated strong cytotoxicity against the normal cell line MRC-5. This paper reports for the first time the cytotoxic activities of C. mangga extracts on KB, A549, Ca Ski, HT-29 and MRC-5, and the occurrence of compound 2 and 3 in C. mangga.