Anand C. Burman

Betulinic Acid Derivatives as Anticancer Agents: Structure Activity Relationship

Betulinic acid, a pentacyclic triterpene, is widely distributed throughout the tropics. It possesses several biological properties such as anticancer, anti-inflammatory, antiviral, antiseptic, antimalarial, spermicidal, antimicrobial, antileshmanial, antihelmentic and antifeedent activities. However, betulinic acid was highly regarded for its anticancer and anti-HIV activities. Anticancer role of betulinic acid appeared by inducing apoptosis in cells irrespective of their p53 status. Due to high order safety in betulinic acid, a number of structural modifications carried out to improve its potency and efficacy. The C-1, C-2, C-3, C-4, C-20 and C-28 positions are the diversity centers in betulinic acid, and the derivatives resulted on various structural modifications at these positions screened for their anticancer activity. This review presents the structure activity relationship carried out on C-1, C-2, C-3, C-4, C-20, C-28, A-ring, D-ring and E-ring modified betulinic acid derivatives. We have compiled the most active betulinic acid derivatives along with their activity profile in each series. Structure activity relationship studies revealed that C-28 carboxylic acid was essential for the cytotoxicity. The halo substituent at C-2 position in betulinic acid enhanced the cytotoxicity. Though the relation of the cytotoxicity with the nature of substituents at C-3 position could not be generalized but the ester functionality appeared to be a better substituent for enhancing the cytotoxicity. An interesting observation is that the three rings skeleton (A, B and C rings) had played an important role in eliciting anticancer activity, which could be a new molecular skeleton to design new anticancer drugs.

Eclipta alba extract with potential for hair growth promoting activity

ETHNOPHARMACOLOGICAL RELEVANCE Eclipta alba is traditionally known to potentiate hair growth promotion. AIM OF THE STUDY The study was aimed to investigate the efficacy of methanol extract of Eclipta alba as hair growth promoter. MATERIALS AND METHODS Pigmented C57/BL6 mice, preselected for their telogen phase of hair growth were used. In these species, the truncal epidermis lacks melanin-producing melanocytes and melanin production is strictly coupled to anagen phase of hair growth. The extract was applied topically to assess telogen to anagen transition. Immunohistochemical investigation was performed to analyze antigen specificity. Animals in anagen phase of hair growth were positive for FGF-7 and Shh and negative for BMP4, whereas the animals in telogen phase were positive only for BMP4 antigen. RESULTS The methanol extract of whole plant when tested for hair growth promoting potential, exhibited dose dependent activity in C57BL6 mice. The activity was assessed by studying the melanogenesis in resected skin, follicle count in the subcutis, skin thickness and surrogate markers in vehicle control and extract treated animals. CONCLUSION These findings suggest that methanol extract of Eclipta alba may have potential as a hair growth promoter.

Protective effects of Terminalia arjuna against Doxorubicin-induced cardiotoxicity

Terminalia arjuna has been marked as a potential cardioprotective agent since vedic period. The present study was aimed to investigate the effects of butanolic fraction of Terminalia arjuna bark (TA-05) on Doxorubicin (Dox)-induced cardiotoxicity. Male wistar rats were used as in vivo model for the study. TA-05 was administered orally to Wistar rats at different doses (0.42 mg/kg, 0.85 mg/kg, 1.7 mg/kg, 3.4 mg/kg and 6.8 mg/kg) for 6 days/week for 4 weeks. Thereafter, all the animals except saline and TA-05-treated controls were administered 20 mg/kg Dox intraperitonially. There was a significant decrease in myocardial superoxide dismutase (38.94%) and reduced glutathione (23.84%) in animals treated with Dox. Concurrently marked increase in serum creatine kinase-MB (CKMB) activity (48.11%) as well as increase in extent of lipid peroxidation (2.55-fold) was reported. Co-treatment of TA-05 and Dox resulted in an increase in the cardiac antioxidant enzymes, decrease in serum CKMB levels and reduction in lipid peroxidation as compared to Dox-treated animals. Electron microscopic studies in Dox-treated animals revealed mitochondrial swelling, Z-band disarray, focal dilatation of smooth endoplasmic reticulum (SER) and lipid inclusions, whereas the concurrent administration of TA-05 led to a lesser degree of Dox-induced histological alterations. These findings suggest that butanolic fraction of Terminalia arjuna bark has protective effects against Dox-induced cardiotoxicity and may have potential as a cardioprotective agent.

Synthesis and cytotoxic activity of heterocyclic ring-substituted betulinic acid derivatives.

A new series of betulinic acid derivatives have been synthesized by introducing heterocyclic ring between C-2 and C-3 positions of betulinic acid. Further modifications were also carried out by reduction of C-20(29) unsaturated bond and substitution of C-28 carboxyl group by ester and amide linkage to enhance the selectivity. Compound 11 resulted in IC(50) of 2.44, 2.5, and 2.7 microg/ml on MIAPaCa, PA-1, and SW620 cancer cell lines, respectively. Compound 38 resulted in IC(50) of 0.67 microg/ml on MIAPaCa cell line.

1,8-Naphthyridine-3-carboxamide derivatives with anticancer and anti-inflammatory activity.

A number of 1-propargyl-1,8-naphthyridine-3-carboxamide derivatives (15-35) have been synthesized and screened for their in vitro cytotoxicity and anti-inflammatory activity. Compounds 22, 31 and 34 have shown high cytotoxicity against a number of cancer cell lines, while compound 24 showed significant anti-inflammatory activity.

Synthesis of quinazolines as tyrosine kinase inhibitors.

In the present review, the discovery and development of quinazoline as tyrosine kinase inhibitors has been described. The synthesis of most potent quinazoline inhibitors of EGFR, VEGFR and PDGRF has been discussed. Structure activity relationship for quinazoline as tyrosine kinase inhibitors has been established. It was found that C-4, C-6 and C-7 positions in quinazoline are appropriate sites for designing new tyrosine kinase inhibitors. This review should help the medicinal chemist in designing more effective tyrosine kinase inhibitors.

Synthesis of functionalized amino acid derivatives as new pharmacophores for designing anticancer agents

A new series of functionalized amino acid derivatives N-substituted 1-N-(tert-butoxycarbonyl)-2,2-dimethyl-4-phenyl-5-oxazolidine carboxamide (1-17) and 1-N-substituted-3-amino-2-hydroxy-3-phenylpropane-1-carboxamide (18-34) were synthesized and evaluated for their in vitro cytotoxicity against human cancer cell lines. Compound 6 has shown interesting cytotoxicity (IC50 = 5.67 μm) in ovarian cancer, while compound 10 exhibited promising cytotoxicity in ovarian (IC50 = 6.1 μm) and oral (IC50 = 4.17 μm) cancers. These compounds could be of use in designing new anti-cancer agents.

Anticancer and immunomodulatory activities of novel 1,8-naphthyridine derivatives

A number of 1,8-naphthyridine derivatives (22–62) have been synthesized and screened for their in vitro cytotoxicity against eight tumors and two non-tumor cell lines. Halogen substituted 1,8-naphthyridine-3-caboxamide derivatives showed potent activity with compound 47 having IC50 of 0.41 and 0.77 μM on MIAPaCa and K-562 cancer cell lines, respectively while, compound 36 had IC50 of 1.19 μM on PA-1 cancer cell line. However, one of the unsubstituted 1,8-naphthyridine-C-3’-heteroaryl derivative 29 showed potent cytotoxicity with IC50 of 0.41 and 1.4 μM on PA-1 and SW620 cancer cell lines, respectively. These compounds were also evaluated for anti-inflammatory activity as suggested by downregulation of proinflammaotory cytokines.

Anticancer activity of a peptide combination in gastrointestinal cancers targeting multiple neuropeptide receptors.

SummaryA novel peptide combination consisting of four synthetic neuropeptide analogs of Vasoactive Intestinal Peptide (VIP), Bombesin, Substance P and Somatostatin has been found to have potent anticancer activity in vitro and in vivo. The receptors of these four neuropeptides are known to be over expressed in various cancers. We have found the presence of native neuropeptides in the culture supernatant of the primary tumor cells of human colon adenocarcinomas. It was further demonstrated by receptor-ligand assays that not only do these tumor cells synthesize and secrete four peptide hormones but also possess specific high affinity receptors on their surface. Screening a large panel of analogs to the four peptide hormones on tumor cell proliferation led to the identification of four cytotoxic analogs, the combination of which was code-named DRF7295. The design and synthesis of the peptide analogs have been described in this paper. In vitro anticancer activity of DRF7295 was studied in a large panel of human tumor cells. Gastrointestinal tumor cells of the colon, pancreas and duodenum were found to be most sensitive to DRF7295 with moderate activity seen in glioblastoma, prostate, leukemia and those of oral cancer cells. Efficacy studies in xenograft models of colon and duodenum resulted in T/C% of less than 40%, which is indicative of strong tumor regressing potential of DRF7295 in gastrointestinal cancers. Acute and long-term toxicity studies as well as safety pharmacology studies conducted indicate the safety of the drug upon systemic administration with no significant adverse pharmacological effects.

Modulation of key signal transduction molecules by a novel peptide combination effective for the treatment of gastrointestinal carcinomas

SummaryWe have reported earlier a novel combination of four structurally designed synthetic neuropeptide analogs of vasoactive intestinal peptide (VIP), bombesin, substance P and somatostatin, code-named DRF 7295 which have anti-tumor efficacy for adenocarcinomas in vitro and in vivo (Jaggi et al., Invest New Drugs, 2008). The discovery, synthesis, in vitro and in vivo efficacy was reported (Jaggi et al., Invest New Drugs, 2008). Gastrointestinal tumor cells of the colon, pancreas and duodenum were found to most sensitive to DRF7295 in vitro and in vivo (Jaggi et al., Invest New Drugs, 2008). We have further investigated and report here the modulation of cellular signaling in gastrointestinal carcinomas by DRF 7295, which may be mediating its observed anticancer activity in these cancer types. DRF 7295 inhibits the binding of specific neuropeptides initiating a cascade of cellular signaling events leading to programmed cell death. It down regulates the second messenger cAMP, epidermal growth factor (EGF) dependent proliferation and the phosphorylated MAP Kinase pERK1/2 in gastrointestinal carcinomas, thus depriving the tumour cells of critical pro-proliferative cellular signals. It triggers bcl2 and Caspase 3 dependent apoptotic cell death and induces p53 tumor suppressor protein in the treated carcinoma cells in vitro. It has significant anti-angiogenic potential as reflected in the inhibition of tube like formation in the endothelial cells and down regulation of VEGF levels. Tumour xenograft studies confirmed the in vivo efficacy of DRF 7295 for gastrointestinal carcinomas (Jaggi et al., Invest New Drugs, 2008). The Phase I clinical trials have shown DRF 7295 to be well tolerated and devoid of systemic toxicities of the conventional cytotoxics (Mukherjee et al., Phase I dose escalating study of DRF7295: a new class of peptide based drugs. “Abstract” ASCO ID:948, 2003). The drug may have a promising role in disease stabilization in colorectal and other cancers. Thus DRF 7295 is a novel targeted drug in the class of signal transduction modulators, with potential for treatment of gastrointestinal carcinomas.