Isolation and Enzyme‐Inhibition Studies of the Chemical Constituents from Ajuga bracteosa

Bractin A (=(2 S ,3 S ,4 R ,5 E )‐2‐{[(2 R )‐2‐hydroxydodecanoyl]amino}triacont‐5‐ene‐1,3,4‐triol; 1 ) and bractin B (=(2 S ,3 S ,4 R ,5 E ,8 E )‐2‐{[(2 R ) ‐ 2‐hydroxyhexacosanoyl]amino}pentadeca‐5,8‐diene‐3,4,15‐triol 1‐ O ‐ β ‐ D ‐glucopyranoside; 2 ), new sphingolipids, and bractic acid (=(5 Z ,10 Z ,15 Z )‐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 μ M 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 μ M , for lipoxygenase, acetylcholinesterase, and butyrylcholinesterase, respectively.