Synthetic and antimicrobial studies on natural cyclopolypeptide from Caribbean marine-sponge and its analogs

Objective: A natural cyclic peptide, rolloamide, previously isolated from marine-sponge, was synthesized by coupling of tri and tetrapeptide units Boc­Phe-Pro- Val­OMe and Boc­Pro-Leu-Pro-Ile­OMe after proper deprotection at carboxyl and amino terminals followed by cyclization of linear heptapeptide segment. Design and Methodology: Solution phase technique was adopted for the synthesis of cycloheptapeptide. Required tri and tetrapeptide units were prepared by coupling of Boc-protected dipeptides viz. Boc­Phe-Pro­OH and Boc­Pro-Leu­OH with respective amino acid methyl ester hydrochloride Val-OMe.HCl and dipeptide methyl ester Pro-Ile-OMe. Cyclization of linear heptapeptide unit was done by p-nitrophenyl ester method. Similarly, two analogs of rolloamide were prepared by modification of tripeptide unit. The structures of synthesized cyclopeptide and its analogs were elucidated by spectral and elemental analysis. The newly synthesized peptide was subjected to antimicrobial screening and compared with biopotential of analogs. Results: Synthesis of cyclopeptide was accomplished with >84% yield utilizing diisopropylcarbodiimide (DIPC) as coupling agent. Newly synthesized peptide possessed promising activity against C. albicans and P. aeruginosa, K. pneumonia as compared to standard drugs, in addition to moderate activity against dermatophytes. Synthesized peptide analogs showed better antimicrobial potential against C. albicans and dermatophytes. Conclusions: Solution phase technique employing N,Ndiisopropylcarbodiimide (DIPC) and triethylamine (TEA) proved to be effective for the synthesis of natural cycloheptapeptide. N-methyl morpholine (NMM) was found to be a better base for cyclization of linear heptapeptide unit in comparison to TEA and pyridine. Promising antimicrobial potential was seen for newly synthesized cyclic peptide and its analogs.

Morphological, pathological and molecular variability in Botryodiplodia theobromae (Botryosphaeriaceae) isolates associated with die-back and bark canker of pear trees in Punjab, India.

Thirteen isolates of Botryodiplodia theobromae collected from pear varieties grown in various regions of Punjab were studied for morphological, pathological and molecular characterization. The mycelial growth of B. theobromae isolates was classified as fluffy or depressed, uniform to irregular and cottony white turning to black. Colony growth rate varied from 19.1 to 24.9 mm per day. Pycnidia were produced either on the edge, centered or scattered on Petri dishes after 20 to 34 days of incubation. Pycnidia and pycnidiospores ranged in size from 118.0 to 240.0 microm and 14.5-35.5 x 6.5-14.5 microm, respectively. Lesion length produced by different isolates ranged from 1.9-7.2 x 0.8-3.3 cm with 49.4-90.9% infection. Using nine SSR and seven RAPD markers, amplified DNA bands ranged from 0.2 to 1.5 and 0.18 to 2.0 kb, respectively. Polymorphism information content values ranged from 0.44 to 0.71 and 0.63 to 0.93 for SSR and RAPD markers, respectively. A dendrogram based on molecular data, grouped the isolates into three major clusters with 65 to 79.5% genetic similarity; most of the isolates showed variety-specific grouping. The isolates prevalent on pear cultivars 'Patharnakh' and 'Baggugosha' in Ludhiana, Amritsar and Hoshiarpur districts were found to have a high degree of similarity; these isolates were also considerably distant from mango isolates and from other isolates on other pear cultivars. The isolates from cultivars Punjab Beauty, LeConte and Kieffer also had a high degree of similarity. Isolates from cultivar Smith were different from other pear isolates but showed more similarity with mango isolates.