4-O-Methyl honokiol is a natural neolignan isolated from Magnolia officinalis , acts as a PPARγ agonist, and inhibtis NF-κB activity. 4-O-Methyl honokiol (20 μM) increases the expression, transcription and DNA binding activities, and nuclear translocation of PPARγ in both in prostate PC-3 and LNCap cells. 4-O-Methyl honokiol (0-30 μM) inhibits LNCaP and PC-3 cancer cells growth, causes G0/G1 phase arrest and induces apoptotic cell death, and such effects can be reversed by PPARγ antagonist. 4-O-Methyl honokiol inhibits NF-κB activity and cancer cell growth, but such effects as well as its activation of PPARγ can be abolished by knock-down of p21. 4-O-methylhonokiol (0.5, 1 and 2 μM) reduces LPS-induced release of NO, PGE2, ROS, TNF-α and IL-1β in cultured astrocytes, and amyloidogenesis in cultured astrocytes and microglial BV-2 cells.

4-O-Methyl honokiol (40 or 80 mg/kg, i.p. everyday for 4 weeks) inhibits the growth of SW620 and PC3 tumours in SW620 and PC3 xenograft model. 4-O-Methyl honokiol significantly increases the expression of p21 and PPARγ in the tumour tissues. 4-O-Methyl honokiol (0.5 or 1 mg/kg/day daily for 3 weeks) significantly ameliorates LPS-induced memory impairment, and inhibits LPS-induced iNOS and COX-2 expression in mice. 4-O-Methyl honokiol also shows inhibitory activities against the Aβ _1-42 accumulation, and activates astrocytes and microglia in LPS-injected mice brain.