Discovery of Novel Anti-cryptosporidial Activities From Natural Products by in vitro High-Throughput Phenotypic Screening

Abstract

Cryptosporidium parvum is a globally distributed zoonotic protozoan parasite of both medical and veterinary importance. Nitazoxanide is the only FDA-approved drug to treat cryptosporidiosis in immunocompetent people, but it is not fully effective. There is no drug approved by FDA for use in immunocompromised patients or in animals. In the present study, we conducted phenotypic screening of 800 nature products with defined chemical structures for potential novel activity against the growth of C. parvum in vitro. We identified a large number of compounds showing low to sub-micromolar anti-cryptosporidial activity, and fully characterized 16 top hits for anti-parasitic efficacies in vitro [EC50 values from 0.122 to 3.940 μM, cytotoxicity (TC50) values from 6.31 to >100 μm] and their safety margins. Among them, 11 compounds were derived from plants with EC50 values from 0.267 to 3.940 μM [i.e., cedrelone, deoxysappanone B 7,4′-dimethyl ether (Deox B 7,4), tanshinone IIA, baicalein, deoxysappanone B 7,3′-dimethyl ether acetate, daunorubicin, dihydrogambogic acid, deacetylgedunin, deacetoxy-7-oxogedunin, dihydrotanshinone I, 2,3,4′-trihydroxy-4-methoxybenzophenone, and 3-deoxo-3beta-hydroxy-mexicanolide 16-enol ether]. Three compounds with sub-micromolar EC50 values (i.e., cedrelone, Deox B 7,4, and baicalein) were further investigated for their effectiveness on various parasite developmental stages in vitro. Cedrelone and baicalein were more effective than Dexo B 7,4 when treating parasite for shorter periods of time, but all three compounds could kill the parasite irreversibly. These findings provide us a large selection of new structures derived from natural products to be explored for developing anti-cryptosporidial therapeutics.

Therapeutic potential of Commiphora molmol extract loaded on chitosan nanofibers against experimental cryptosporidiosis

“…The noted observation emerging from the compared data was that Cm-CsNFs (100 mg/kg) is more effective against oocyst and trophozoite of Cryptosporidium than NTZ, which is the mainline, standard treatment for infection in adults and children [8] . Also the chitosan loaded C. molmol gave better result than the sole extract C. molmol despite the high dose used (500 mg/kg).…”

“…Presently, the available medications are not entirely successful against cryptosporidiosis [7] . Nitazoxanide is the only FDA-approved drug used for the treatment in immunocompetent persons, although it is not entirely effective [8] . Besides NTZ, a few other commercial medications are not FDA-approved for the treatment [9] .…”

Walsura robusta Roxb. (Meliaceae), a little-known tree with a rich limonoid profile

“…Cedrolone is an interesting natural product which also displays anti-fungal and insecticidal activities (Govindachari et al, 1995(Govindachari et al, , 2000. It exhibits a sub-micromolar activity against the protozoan parasite Cryptosporidium parvum in vitro (EC 50 = 0.27 µM) (Jin et al, 2019) and causes lethal and sublethal effects on the armyworm Spodoptera frugiperda (Giongo et al, 2016).…”

The immunomodulatory activity of secnidazole–nitazoxanide in a murine cryptosporidiosis model

“…Further, in the developing world and resource-constrained countries, ART is not suitable, as it is too expensive and not readily accessible or affordable. Hence there is a persistent need to find new and effective anti-cryptosporidial agents that will also benefit cancer and post-transplant patients [16]. Secnidazole (SEC; Amebazole) is a synthetic derivative of the nitroimidazoles group.…”