Panneerselvam Yuvaraj

Bio-prospecting of soil Streptomyces and its bioassay-guided isolation of microbial derived auxin with antifungal properties

The present study was aimed to isolate bioactive actinomycetes with antifungal properties. Twenty-seven distinct soil derived actinomycetes were investigated for their antifungal activities. Among these, one isolate exhibited significant antifungal activity. Phenotypic and 16s rRNA gene sequence analysis strongly suggested that the active isolate BG4 belonged to the genus Streptomyces. Further, the chemical investigation of the active extract resulted in the isolation of a major compound and it was structurally elucidated as phenyl acetic acid (PAA). PAA exhibited promising antifungal activity with 100% inhibition, ranging from 31.25 to 25μg/mL. It is to be noted that PAA is naturally occurring and biologically active auxin. In addition, it has also been hypothesized that phytohormone endorsing the source of soil-symbionts has similar pathways for synthesizing compounds and its congeners of host due to horizontal gene transfer. These findings demonstrate that microbially derived phytohormone can be used to treat fungal infections.

(4S)-5′-Chloro-3,7,7-trimethyl-5,6,7,8-tetra­hydro-4H-spiro­[1,2-oxazolo[5,4-b]quinoline-4,3′-indole]-2′,5-dione

In the title compound, C20H18ClN3O3, the five- and six-membered heterocycles fused through a spiro C atom are inclined to each other at an angle of 87.4 (1)°. In the tricyclic ring system, the cyclohexene ring adopts an envelope conformation with the spiro atom as the flap. In the crystal, two sets of N—H⋯O hydrogen bonds link the molecules into columns containing centrosymmetric R 2 2(7) ring motifs and propagating along the b-axis direction.

Methyl 2-(5-chloro-1-methyl-2-oxo-2,3-di-hydro-1H-indol-3-ylidene)acetate.

The title compound, C12H10ClNO3, the indoline ring system is essentially planar, with a maximum deviation of 0.009 Å for the N atom. The indoline ring and acetate group are essentially coplanar, with a maximum deviation of 0.086 Å for the O atom. The mean plane through the methoxycarbonylmethyl group forms a dihedral angle of 3.68 (5)° with the plane of the indoline ring system. The molecular structure is stabilized by an intramolecular C—H⋯O hydrogen-bond interaction. In the crystal, π–π stacking interactions [centroid–centroid distance = 3.7677 (8) Å] occur between benzene rings, forming a chain running along the c-axis direction.

2-Chloro-8,8-dimethyl-8,9-dihydro-7H-chromeno[2,3-b]quinoline-10,12-dione.

The asymmetric unit of the title compound, C18H14ClNO3, contains two independent molecules (A and B). In both molecules, the cyclohexanone ring has a chair conformation. The dihedral angles between the pyran ring and the pyridine and chlorophenyl rings are 2.13 (9) and 2.19 (9)°, respectively, in A, and 0.82 (9) and 1.93 (9)°, respectively, in B. The carbonyl O atoms deviate from the pyran and benzene rings to which they are attached by −0.092 (2) and 0.064 (2) Å, respectively, in A, and by −0.080 (2) and −0.063 (2) Å, respectively, in B. In the crystal, the A molecules are linked via C—H⋯O hydrogen bonds, forming double-stranded chains along [100]. They lie parallel to the double-stranded chains formed by the B molecules, which are also linked via C—H⋯O hydrogen bonds. The chains stack up the c axis in an –A–A–B–B–A–A– manner, with a number of π–π interactions involving A and B molecules; the centroid–centroid distances vary from 3.4862 (11) to 3.6848 (11) Å

Methyl (3S,10b'S)-5-chloro-9′-fluoro-1-methyl-2-oxo-5′-phenyl-10b'H-spiro­[indoline-3,1′-pyrazolo­[3,2-a]iso­quinoline]-2′-carboxyl­ate

In the title compound, C27H19ClFN3O3, the pyrazole ring has a twist conformation and the six-membered ring to which it is fused has a screw-boat conformation. The mean plane of the pyrazole ring is inclined to the 2-methylindoline ring by 85.03 (9) and by 28.17 (8)° to the mean plane of the isoquinoline ring system. In the crystal, molecules are linked by pairs of C—H⋯F hydrogen bonds, forming inversion dimers. These dimers are linked via C—H⋯O hydrogen bonds, forming a two-dimensional network lying parallel to (10-1).

A diastereomer of methyl (1R,3'S)-1',1''-dimethyl-2,2''-dioxo-2H-dispiro-[ace-naphthyl-ene-1,2'-pyrrolidine-3',3''-indoline]-4'-carboxyl-ate.

In the title compound, C26H22N2O4, the central pyrrolidine ring adopts a twist conformation and the cyclopentane ring of the dihydroacenapthylene group adopts an envelope conformation with the spiro C atom as the flap. The naphthalene ring system of the dihydroacenaphthylene group forms dihedral angles of 83.4 (9) and 61.3 (7)°, respectively, with the mean planes of the pyrrolidine and indole rings. The crystal packing is stabilized by intermolecular C—H⋯O hydrogen bonds. The title compound is a diastereomer of a previously reported structure.

8,8-Dimethyl-8,9-dihydro-7H-chromeno[2,3-b]quinoline-10,12-dione

In the title compound, C18H15NO3, the fused benzopyran and pyridine rings are essentially coplanar [r.m.s. deviation = 0.0533 Å with a maximum deviation of 0.080 (1) Å for a benzene C atom]. The cyclohexanone ring adopts an envelope conformation with the dimethyl-substituted C atom 0.660 (2) Å out of the plane formed by the remaining ring atoms (r.m.s. deviation = 0.0305 Å). The dihedral angle between the mean planes of the pyran and cyclohexanone rings is 12.95 (6)°. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, leading to chains running along [011].