Matrine-DTC Hybrids: A Promising Anti-Cancer Drug Development

Cancer remains a global health concern, and its impact extends far beyond geographical boundaries. According to the World Health Organization (WHO), cancer is the second leading cause of death worldwide, responsible for nearly 10 million deaths in 2020. It is estimated that one in six deaths globally is due to cancer. The escalating cancer incidence is a grave concern, demanding innovative solutions from the scientific community. Pharmaceutical chemists have tirelessly pursued the development of anticancer agents, resulting in a plethora of promising compounds. However, substantial challenges, including low selectivity, adverse toxic side effects, and the emergence of multidrug resistance, have proven formidable obstacles to overcome. One interesting natural product named matrine, the principal component of Sophora flavescens Aiton, has demonstrated its ability to inhibit tumor cell proliferation. Nevertheless, its clinical application remains hindered by limitations such as low water solubility, poor bioavailability, and toxic side effects. The family of dithiocarbamate (DTC)-containing molecules, exemplified by brassinin, has exhibited diverse physiological activities, providing a tantalizing avenue for anticancer drug development. Notably, chalcone-DTC, synthesized by introducing DTC into the chalcone molecule, and thalidomide-DTC, created by integrating DTC into thalidomide, have both shown increased inhibitory activity against cancer cells.

Nature has provided invaluable source of therapeutic agents, with more than 80 of the 371 pharmaceutical monographs in the Ninth Edition of the International Pharmacopoeia derived from natural products and their derivatives. Astonishingly, over 60% of existing anticancer agents are derived from natural product derivatives. Consequently, natural products present an intriguing resource for the development of novel therapies for a wide spectrum of diseases, including cancer. The amalgamation of distinct biologically active pharmacophores through the “molecular hybridization strategy” represents a potent approach for crafting highly effective antitumor drug candidates. In light of this, the fusion of DTC with matrine holds promise for the creation of derivatives endowed with exceptional antitumor activity. To this end, a new study published in the European Journal of Medicinal Chemistry conducted by Dr. Meng-Wei Zhang, Dr. Yu He, and Dr. Meng-Xue Wei from the College of Chemistry and Chemical Engineering at Ningxia University developed a one-pot, three-step synthesis strategy to generate a series of matrine-DTC hybrids and rigorously assessed their in vitro cytotoxic activity and mode of action.

The research team synthetic strategy began with the hydrolysis of matrine in aqueous potassium hydroxide, yielding product 1. This compound was subsequently esterified using a mixture of sulphoxide chloride and a primary alcohol (methanol or ethanol) to generate crude products 2. A “one-pot reaction” with carbon disulphide and halogenated hydrocarbons in chloroform followed, yielding matrine-DTC hybrids 4a–4f with an overall yield ranging from 33% to 58% over two steps. Unfortunately, replacing the primary alcohol with a secondary alcohol (L-menthol or isoborneol) in the above procedure yielded no products, likely attributable to the weak reactivity of secondary alcohols. To surmount this challenge, the authors first reacted product 1 with carbon disulphide, halogenated hydrocarbons, and potassium phosphate in chloroform to yield intermediates 3. These intermediates were subsequently condensed with L-menthol or isoborneol to generate matrine-DTC hybrids 4g–4l through a two-step process, yielding 34% to 48% overall. It is noteworthy to mention, the existence of matrine-DTC hybrids had not been previously reported, underscoring the novelty of the new study. The structures of all matrine-DTC hybrids were meticulously confirmed through ¹H, ¹³C NMR and ¹⁹F NMR spectroscopy, HRMS, and FT-IR spectroscopy.

The authors systematically evaluated the in vitro cytotoxicity of the synthesized matrine-DTC hybrids (4a–4l) and compared to both matrine and vincristine (VCR), which served as references. Remarkably, all matrine-DTC hybrids exhibited significantly greater toxicity towards human hepatoma cells HepG2 when compared to the parent matrine (IC50 > 4900 μM). Among these hybrids, 4l emerged as the most potent, with an IC50 value of 31.39 μM against HepG2 cells and the highest selectivity (SI = HEK-293T/HepG2 ≈ 6), surpassing that of VCR (SI ≈ 1) and matrine (SI ≈ 1). Notably, when R1 was menthyl or bornyl, the hybrids (4g–4l) displayed superior toxicity (IC50 = 31.39–90.68 μM) compared to when R1 was methyl or ethyl (4a–4f, IC50 = 147.78–262.45 μM) against human hepatoma cells. This enhanced potency was also superior to that of the reference VCR (IC50 = 93.67 μM). Additionally, the hybrids 4f and 4l, containing 4-(trifluoromethyl)benzyl as R2, demonstrated the highest selectivity (SI ≈ 6), further outperforming matrine and VCR.

The superiority of hybrid 4l was underscored by its remarkable cytotoxicity against various other human cancer cells, including lung cancer cells (Calu-1), breast cancer cells (SK-BR-3), liver cancer cells (HUH-7), renal cell carcinoma cells (786-O), and ovarian cancer cells (SK-OV-3). Notably, this heightened toxicity was accompanied by relatively lower toxicity towards corresponding normal cells (WI-38, LX-2, HEK-293T, and KGN), further substantiating the potential of hybrid 4l as an anti-hepatocellular carcinoma agent. To elucidate the mechanism underlying the observed cytotoxicity, the authors conducted a series of experiments. As the concentration of hybrid 4l increased, there was a corresponding rise in the inhibition rate against HepG2 cells, as well as observable changes in cell morphology, characterized by volume reduction, chromatin margination, and the formation of apoptotic vesicles. Flow cytometry using Annexin V-FITC/PI confirmed the induction of apoptosis by hybrid 4l in HepG2 cells in a concentration-dependent manner.

In summary, Ningxia University scientists successfully synthesized twelve novel matrine-DTC hybrids through a concise three-step synthetic strategy. These hybrids exhibited remarkable in vitro cytotoxicity against human hepatoma cells, with hybrid 4l standing out as the most potent candidate, outperforming both matrine and VCR. Moreover, hybrids 4f and 4l displayed exceptional selectivity, making them highly promising candidates for further exploration as anti-hepatocellular carcinoma drugs. The new study underscores the potential of molecular hybridization as a viable strategy for creating novel anticancer agents and offers new hope in the ongoing battle against cancer.