Ravi P. Reddy

Bio: Ravi P. Reddy is an academic researcher. The author has contributed to research in topics: Amodiaquine & Peptide. The author has an hindex of 2, co-authored 3 publications receiving 550 citations.

Discovery of Trp-His and His-Arg analogues as new structural classes of short antimicrobial peptides.

Abstract: Naturally occurring antimicrobial peptides contain a large number of amino acid residues, which limits their clinical applicability. In search of short antimicrobial peptides, which represent a possible alternative for lead structures to fight antibiotic resistant microbial infections, a series of synthetic peptide analogues based on Trp-His and His-Arg structural frameworks have been prepared and found to be active against several Gram-negative and Gram-positive bacterial strains as well as against a fungal strain with MIC values of the most potent structures in the range of 5-20 microg/mL ((IC(50) in the range of 1-5 microg/mL). The synthesized peptides showed no cytotoxic effect in an MTT assay up to the highest test concentration of 200 microg/mL. A combination of small size, presence of unnatural amino acids, high antimicrobial activity, and absence of cytotoxicity reveals the synthesized Trp-His and His-Arg analogues as promising candidates for novel antimicrobial therapeutics.

Quinolines and Structurally Related Heterocycles as Antimalarials

Abstract: The quinoline scaffold is prevalent in a variety of pharmacologically active synthetic and natural compounds. The discovery of chloroquine, the most famous drug containing this scaffold resulted in control and eradication of malaria for decades. The other known antimalarial drugs from the quinoline family include: quinine, amodiaquine, piperaquine, primaquine, and mefloquine. The drugs from this group mostly act during the blood stages of the parasite’s life cycle but some like primaquine targets the tissue stages. This review provides a comprehensive literature compilation concerning the study of quinolines and also other heterocycles structurally similar to quinoline scaffold in the treatment of malaria. This review covers advances made in the last ten years and it is subdivided into eight sub-headings. It consists of discussion on the biological activities, structure–activity relationship, and potential biochemical pathways of 4-aminoquinolines, 4-anilinoquinolines, 8-aminoquinolines, quinolines from nature, quinolones, isoquinolines and tetrahydroquinolines, ring-modified quinolines, and miscellaneous quinolines.

Quinoline as a Privileged Scaffold in Cancer Drug Discovery

Abstract: Quinoline (1-azanaphthalene) is a heterocyclic aromatic nitrogen compound characterized by a double-ring structure that contains a benzene ring fused to pyridine at two adjacent carbon atoms. Quinoline compounds are widely used as "parental" compounds to synthesize molecules with medical benefits, especially with anti-malarial and anti-microbial activities. Certain quinoline-based compounds also show effective anticancer activity. This broad spectrum of biological and biochemical activities has been further facilitated by the synthetic versatility of quinoline, which allows the generation of a large number of structurally diverse derivatives. This includes numerous analogues derived from substitution of the quinoline ring system, and derivatization of quinoline ring structure. Quinoline and its analogs have recently been examined for their modes of function in the inhibition of tyrosine kinases, proteasome, tubulin polymerization and DNA repair. In this review, we have summarized our knowledge on quinoline compounds with respect to their anticancer activities, mechanisms of action, structure-activity relationship (SAR), and selective and specific activity against various cancer drug targets. In particular, we focus our review on in vitro and in vivo anticancer activities of quinoline and its analogs in the context of cancer drug development and refinement.

Antimicrobial peptides: Promising alternatives in the post feeding antibiotic era.

Abstract: Antimicrobial peptides (AMPs), critical components of the innate immune system, are widely distributed throughout the animal and plant kingdoms. They can protect against a broad array of infection-causing agents, such as bacteria, fungi, parasites, viruses, and tumor cells, and also exhibit immunomodulatory activity. AMPs exert antimicrobial activities primarily through mechanisms involving membrane disruption, so they have a lower likelihood of inducing drug resistance. Extensive studies on the structure-activity relationship have revealed that net charge, hydrophobicity, and amphipathicity are the most important physicochemical and structural determinants endowing AMPs with antimicrobial potency and cell selectivity. This review summarizes the recent advances in AMPs development with respect to characteristics, structure-activity relationships, functions, antimicrobial mechanisms, expression regulation, and applications in food, medicine, and animals.

The antimalarial ferroquine: role of the metal and intramolecular hydrogen bond in activity and resistance.

Abstract: Inhibition of hemozoin biocrystallization is considered the main mechanism of action of 4-aminoquinoline antimalarials including chloroquine (CQ) but cannot fully explain the activity of ferroquine (FQ) which has been related to redox properties and intramolecular hydrogen bonding. Analogues of FQ, methylferroquine (Me-FQ), ruthenoquine (RQ), and methylruthenoquine (Me-RQ), were prepared. Combination of physicochemical and molecular modeling methods showed that FQ and RQ favor intramolecular hydrogen bonding between the 4-aminoquinoline NH group and the terminal amino group in the absence of water, suggesting that this structure may enhance its passage through the membrane. This was further supported by the use of Me-FQ and Me-RQ where the intramolecular hydrogen bond cannot be formed. Docking studies suggest that FQ can interact specifically with the {0,0,1} and {1,0,0} faces of hemozoin, blocking crystal growth. With respect to the structure-activity relationship, the antimalarial activity on 15 different P. falciparum strains showed that the activity of FQ and RQ were correlated with each other but not with CQ, confirming lack of cross resistance. Conversely, Me-FQ and Me-RQ showed significant cross-resistance with CQ. Mutations or copy number of pfcrt, pfmrp, pfmdr1, pfmdr2, or pfnhe-1 did not exhibit significant correlations with the IC50 of FQ or RQ. We next showed that FQ and Me-FQ were able to generate hydroxyl radicals, whereas RQ and me-RQ did not. Ultrastructural studies revealed that FQ and Me-FQ but not RQ or Me-RQ break down the parasite digestive vacuole membrane, which could be related to the ability of the former to generate hydroxyl radicals.

Quinoline Drug–Heme Interactions and Implications for Antimalarial Cytostatic versus Cytocidal Activities

Abstract: Historically, the most successful molecular target for antimalarial drugs has been heme biomineralization within the malarial parasite digestive vacuole. Heme released from catabolized host red blood cell hemoglobin is toxic, so malarial parasites crystallize heme to nontoxic hemozoin. For years it has been accepted that a number of effective quinoline antimalarial drugs (e.g., chloroquine, quinine, amodiaquine) function by preventing hemozoin crystallization. However, recent studies over the past decade have revealed a surprising molecular diversity in quinoline-heme molecular interactions. This diversity shows that even closely related quinoline drugs may have quite different molecular pharmacology. This paper reviews the molecular diversity and highlights important implications for understanding quinoline antimalarial drug resistance and for future drug design.