Isolation and enzyme-inhibition studies of the chemical constituents from Ajuga bracteosa.
Bractin A (=(2S,3S,4R,5E)-2-{[(2R)-2-hydroxydodecanoyl]amino}triacont-5-ene-1,3,4-triol; 1) and bractin B (=(2S,3S,4R,5E,8E)-2-{[(2R)-2-hydroxyhexacosanoyl]amino}pentadeca-5,8-diene-3,4,15-triol 1-O-beta-D-glucopyranoside; 2), new sphingolipids, and bractic acid (=(5Z,10Z,15Z)-2-decyl-4,7,8,12,13,17,18-heptahydroxy-20,23-dioxopentacosa-5,10,15-trienoic acid; 3), a long-chain polyhydroxy acid, were isolated from the whole plant Ajuga bracteosa along with four known diterpenoids 4-7. Their structures were deduced by spectral studies including 1D- and 2D-NMR spectroscopy. Compounds 1-3 displayed inhibitory potential against enzyme lipoxygenase, while compounds 4-7 inhibited cholinesterase enzymes in a concentration-dependent manner with IC(50) values in the range 10.0-33.0, 14.0-35.2, and 10.0-19.0 microM for lipoxygenase, acetylcholinesterase, and butyrylcholinesterase, respectively. Lineweaver-Burk, and Dixon plots, and their secondary replots indicated that all compounds exhibit non-competitive type of inhibition with K(i) values in the range of 9.5-35.2, 15.2-36.0, and 11.6-20.5 microM, for lipoxygenase, acetylcholinesterase, and butyrylcholinesterase, respectively.
Riaz
Naheed
N
Pharmaceutical Research Centre, PCSIR Laboratories Complex Karachi, Karachi-75280, Pakistan.
Nawaz
Sarfraz A
SA
Mukhtar
Naveen
N
Malik
Abdul
A
Afza
Nighat
N
Ali
Samar
S
Ullah
Shafi
S
Muhammad
Pir
P
Choudhary
M Iqbal
MI
D031328:Ajuga / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
D004791:Enzyme Inhibitors