MDPI Acta Medica Okayama 1420-3049 24 11 2019 Structural Modifications of Nature-Inspired Indoloquinolines: A Mini Review of Their Potential Antiproliferative Activity EN Ning Wang Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University Marta Świtalska Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences Li Wang Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University Elkhabiry Shaban Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University Md Imran Hossain Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University Ibrahim El Tantawy El Sayed Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University Joanna Wietrzyk Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences Tsutomu Inokuchi Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University Cryptolepine, neocryptolepine and isocryptolepine are naturally occurring indoloquinoline alkaloids with various spectrum of biological properties. Structural modification is an extremely effective means to improve their bioactivities. This review enumerates several neocryptolepine and isocryptolepine analogues with potent antiproliferative activity against MV4-11 (leukemia), A549 (lung cancer), HCT116 (colon cancer) cell lines in vitro. Its activity towards normal mouse fibroblasts BALB/3T3 was also evaluated. Furthermore, structure activity relationships (SAR) are briefly discussed. The anticancer screening of neocryptolepine derivatives was performed in order to determine their cytotoxic and growth inhibitory activities across the JFCR39 cancer cell line panel. No potential conflict of interest relevant to this article was reported.