Limonin is a chemically-induced carcinogenesis inhibitor and HIV-1 replication inhibitor.The human immunodeficiency virus (HIV) is a lentivirus that causes the acquired immunodeficiency syndrome (AIDS).
When culturing the HIV-1 in human peripheral blood mononuclear cells (PBMC) and monocytes/macrophages (M/M), Limonin inhibit the HIV-1 replication in all cellular systems and inhibit HIV-1 replication with EC50 value of 60u μM in PBMC cells in a dose-dependent way [1]. In human hepatoma HepG2 cells, limonin can induced apoptosis, which was evidenced by WB analysis of some apoptosis factors [2].
In the female Syrian hamsters treated with DMBA, which can cause tumor, limonin showed a 60% reduction in tumor burden. It decreased 20% tumor number and 50% tumor mass [3]. In male F344 rats treated with azoxymethane (AOM), 0.05% limonin in diet significantly reduced (65%-92% inhibition) the incidence of colonic adenocarcinoma. Thus, limonin has chemopreventive effects on chemically induced carcinogenesis [4].
References:
[1]. Battinelli L, Mengoni F, Lichtner M, et al. Effect of limonin and nomilin on HIV-1 replication on infected human mononuclear cells. Planta medica, 2003, 69(10): 910-913.
[2]. Langeswaran K, Gowthamkumar S, Vijayaprakash S, et al. Influence of limonin on Wnt signalling molecule in HepG2 cell lines. J Nat Sci Biol Med, 2013, 4(1): 126-133.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3633262/?report=reader
[3]. Miller EG, Fanous R, Rivera-Hidalgo, et al. The effect of citrus limonoids on hamster buccal pouch carcinogenesis. Carcinogenesis, 1989, 10(8): 1535-1537.
[4]. Tanaka T, Kohno H, Tsukio Y, et al. Citrus limonoids obacunone and limonin inhibit azoxymethane-induced colon carcinogenesis in rats. BioFactors (Oxford, England), 2000,  13(1-4): 213-8.