Antimicrobial activity of various parts of Polyalthia longifolia var. pendula: isolation of active principles from the leaves and the berries.

Methanol extracts of leaves, stem, twigs, green berries, flowers, roots, root-wood and root-bark of Polyalthia longifolia var. pendula, were tested for their antibacterial and antifungal potentials. Bioassay monitored isolation work on the methanol extract of leaves and berries which possess promising antibacterial activity led to the isolation of seven clerodane diterpenoids, 16(R and S)-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide (1), 16-oxo-cleroda-3,13(14)E-dien-15-oic acid (2), methyl-16-oxo-cleroda-3,13(14)E-dien-15-oate (3), 2-oxo-kolavenic acid (4), 16 (R and S)-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide-2-one (5), (4-->2)-abeo-16(R and S)-hydroxy-cleroda-2,13(14)Z-dien-15,16-olide-3-al (6), 3beta,16alpha-dihydroxy-cleroda-4(18), 13(14)Z-dien-15,16-olide (7), while kolavenic acid (8) and solidagonal acid (9) were obtained from the root-wood. Diterpenoids 1 and 8 were also obtained from the root-bark. It is the first report of the isolation of 7 and 9 from this source, and clerodane 3 was obtained as a natural product for the first time. Clerodanes 1, 2, 5, 6 and 7 were found to be active antimicrobial agents with MIC values ranging between 7.8 and 500 microg/mL. Diterpenoid 1 emerged as the most active antimicrobial agent. The acetyl derivative (10) of 1 and the methyl derivative (3) of 2 were found to be less active than the parent compounds. A complex of allantoin was also obtained from the berries, which on hydrolysis furnished pure allantoin (11).

Evaluation of the antimicrobial property of Polyalthia longifolia var. pendula: isolation of a lactone as the active antibacterial agent from the ethanol extract of the stem.

Bioassay guided fractionation of the ethanolic extract of Polyalthia longifolia var. pendula stem, which showed promising antibacterial activity against thirteen Gram-positive and nine Gram-negative organisms, furnished (3S,4R)-3,4,5-trihydroxypentanoic acid-1,4-lactone (1) as the active principle. The structure of (1) was established by UV, IR, mass, 1H and 13C NMR as well as 2D NMR spectral studies and the formation of its acetate (1a). On acetylation activity of (1) was markedly reduced. It is synthetically well known and only recently isolated from two plants, however, its antimicrobial activity was not reported earlier. The extract, fractions and pure compounds did not show any remarkable activity against fungi and Mycobacterium fortuitum, and M. smegmatis.