Conessine is a plant steroid alkaloid that acts as a potent and specific antagonist of histamine H3 receptors. Conessine displayed high affinity at both rat and human H3 receptors (pKi = 7.61 and 8.27) and generally high selectivity against other sites, including histamine receptors H1, H2, and H4. Conessine was found to efficiently penetrate the CNS and reach very high brain concentrations. Although the very slow CNS clearance and strong binding to adrenergic receptors discouraged focus on conessine itself for further development, its potency and novel steroid-based skeleton motivated further chemical investigation. Modification based on introducing diversity at the 3-nitrogen position generated a new series of H3 antagonists with higher in vitro potency, improved target selectivity, and more favorable drug-like properties. Conessine also has high affinity for the adrenergic receptors. Conessine has being shown to possess anti-malarial activity. In India conessine finds therapeutic use for treatment of dysentery and helminthic disorders.

Pafuramidine or DB289, [2,5-bis-(4-amidinophenyl)furan bis-O-methylamidoxime] is a pro-drug of DB75, [2,5-bis(4-amidinophenyl)furan] also known as furamidine. The biotransformation process of DB289 to DB75 in the human liver consists of three O-demethylation reactions catalyzed by the Cyp4F enzyme subfamily and three N-dehydroxylation reactions catalyzed by cytrochrome b5 and NADH-cytochrome b5 reductase. DB289 was studied for therapeutic treatment against human African trypanosomiasis, Pneumocystis pneumonia and malaria. In November 2006, Immtech Pharmaceuticals, Inc. announced that the U.S. Food and Drug Administration (FDA) had granted orphan drug designation for pafuramidine (DB289) to treat Pneumocystis jiroveci pneumonia (PCP), a common life-threatening opportunistic infection in HIV/AIDS and other immunosuppressed patients. Despite the high efficacy of DB289 in patients, the mechanism of action of DB75 is unknown. The mechanism of antimicrobial activity of diamidine compounds is incompletely understood. They undergo active uptake by purine transporter systems in trypanosomes and their mechanism of action may involve interference with DNA-associated enzymes inhibition of heme crystallization11 or/and collapse of the transmitochondrial membrane potential.

Pafuramidine or DB289, [2,5-bis-(4-amidinophenyl)furan bis-O-methylamidoxime] is a pro-drug of DB75, [2,5-bis(4-amidinophenyl)furan] also known as furamidine. The biotransformation process of DB289 to DB75 in the human liver consists of three O-demethylation reactions catalyzed by the Cyp4F enzyme subfamily and three N-dehydroxylation reactions catalyzed by cytrochrome b5 and NADH-cytochrome b5 reductase. DB289 was studied for therapeutic treatment against human African trypanosomiasis, Pneumocystis pneumonia and malaria. In November 2006, Immtech Pharmaceuticals, Inc. announced that the U.S. Food and Drug Administration (FDA) had granted orphan drug designation for pafuramidine (DB289) to treat Pneumocystis jiroveci pneumonia (PCP), a common life-threatening opportunistic infection in HIV/AIDS and other immunosuppressed patients. Despite the high efficacy of DB289 in patients, the mechanism of action of DB75 is unknown. The mechanism of antimicrobial activity of diamidine compounds is incompletely understood. They undergo active uptake by purine transporter systems in trypanosomes and their mechanism of action may involve interference with DNA-associated enzymes inhibition of heme crystallization11 or/and collapse of the transmitochondrial membrane potential.

Fosmidomycin (3-(formylhydroxyamino)-propylphosphonic acid mono-sodium salt, 3-(N-formyl-N-hydroxyamino)-propylphosphonic acid mono-sodium salt, FR-31564) is a potent inhibitor of P. falciparum 1-deoxy-D-xylulose-5-phosphate reductoisomerase (PfDXR), developed by Albert Schweitzer Hospital for P. falciparum malaria treatment. Fosmidomycin was originally isolated as natural antibiotic from Streptomyces lavendulae. Fosmidomycin is active against a broad range of enterobacteria, but not against Gram-positive organisms or anaerobes. Fosmidomycin was developed as far as an early phase II study for the treatment of urinary tract infections by Fujisawa Pharmaceutical Company (Osaka, Japan) in the early eighties, but these trials have been discontinued. In recent clinical studies, it was shown that fosmidomycin is effective in curing uncomplicated Plasmodium falciparum malaria in humans. The treatment was well tolerated and resulted in a fast parasite and fever clearance. However, the high rate of recrudescence precludes the use of fosmidomycin as a monotherapy. In drug combination studies, the synergy of fosmidomycin with clindamycin was observed. Clinical studies with a fosmidomycin-clindamycin combination are currently ongoing.

Meliltoside is a 2-glucosyloxycinnamic acid found in Dendrobium medicinal plants, Ajuga laxmannii, Ajuga chamaecistus ssp. tomentella, and Teloxys graveolens. It demonstrated moderate antiprotozoal and anti-cancer activity in vitro.

Aporeine (Roemerine) is an aporphine alkaloid that can be isolated from many plants such as Annona senegalensis, Turkish Papaver and Rollinialeptopetala. Aporeine has been reported to exhibit antibacterial activity. It has also been demonstrated to have certain antifungal activity. Aporeine showed selective inhibitory effect on Cox-2.

The alkaloids febrifugine was originally isolated from the roots of the Chinese shrub Dichroa febrifuga. Febrifugine showed an antimalarial activity 50-100 times higher than that of quinine. Febrifugine acts by causing an increase in NO production during the immunological response - increased production of NO by febrifugine plays an important role in host defense against malaria infection in mice. Also, febrifugine are known to inhibit prolyl-tRNA synthetase of malaria parasite Plasmodium falciparum.

Amodiaquine is a medication used to treat malaria, including Plasmodium falciparum malaria when uncomplicated. The mechanism of plasmodicidal action of amodiaquine is not completely certain. Like other quinoline derivatives, it is thought to inhibit heme polymerase activity. This results in accumulation of free heme, which is toxic to the parasites. The drug binds the free heme preventing the parasite from converting it to a form less toxic. This drug-heme complex is toxic and disrupts membrane function. The side effects of amodiaquine are generally minor to moderate and are similar to those of chloroquine. Rarely liver problems or low blood cell levels may occur. When taken in excess headaches, trouble seeing, seizures, and cardiac arrest may occur. After oral administration amodiaquine hydrochloride is rapidly absorbed,and undergoes rapid and extensive metabolism to desethylamodiaquine which concentrates in red blood cells. It is likely that desethylamodiaquine, not amodiaquine, is responsible for most of the observed antimalarial activity, and that the toxic effects of amodiaquine after oral administration may in part be due to desethylamodiaquine.

Amodiaquine is a medication used to treat malaria, including Plasmodium falciparum malaria when uncomplicated. The mechanism of plasmodicidal action of amodiaquine is not completely certain. Like other quinoline derivatives, it is thought to inhibit heme polymerase activity. This results in accumulation of free heme, which is toxic to the parasites. The drug binds the free heme preventing the parasite from converting it to a form less toxic. This drug-heme complex is toxic and disrupts membrane function. The side effects of amodiaquine are generally minor to moderate and are similar to those of chloroquine. Rarely liver problems or low blood cell levels may occur. When taken in excess headaches, trouble seeing, seizures, and cardiac arrest may occur. After oral administration amodiaquine hydrochloride is rapidly absorbed,and undergoes rapid and extensive metabolism to desethylamodiaquine which concentrates in red blood cells. It is likely that desethylamodiaquine, not amodiaquine, is responsible for most of the observed antimalarial activity, and that the toxic effects of amodiaquine after oral administration may in part be due to desethylamodiaquine.

Quinacrine was initially developed as an anti-malarial drug marketed under the name Atabrine. Also it was approved for the teratment of ascites, however it was wothdrawn for both indication in 1995 and 2003, respectively. The drug is also used for the treatment of giardiasis, lupus, rheumatoid arthritis, refractory pulmonary effusion and pneumothorax, induce female sterilization etc. Proposed mechanisms of action include DNA intercalation interference with RNA transcription and translation, inhibition of succinate oxidation interference with electron transport, inhibition of cholinesterase, and inhibitor of phospholipase.