Chemical constituents from the stems of Machilus philippinensis Merr. and the neuroprotective activity of cinnamophilin

Abstract

The Machilus genus (Lauraceae) had been extensively utilized in folk medicine due to its broad range of bioactivities. In the present study, a series of chromatographic separations of the methanol extract of stems of M. philippinensis led to the identification of thirty eight compounds totally. Among these, biscinnamophilin (1), machilupins A-C (2-4), machilutone A (5), and machilusoxide A (6) were new compounds reported for the first time. In addition, 5 was characterized with a unprecedented carbon skeleton. Other known compounds, including the major compounds cinnamophilin (7) and meso-dihydroguaiaretic acid (8), are identified by comparison of their physical and spectroscopic data with reported values. One of the reported compounds, cinnamophilin A (10), should be revised as dehydroguaiaretic acid (9) after careful comparison of all the ¹H and ¹³C NMR data. Moreover, the neuroprotective activity of cinnamophilin (7) was examined in a primary cortical neuron culture and the results indicated that 7 was effective against glutamate induced excitotoxicity.

Fig. 1. Chemical structures of new compounds 1–6 and 7.

Fig. 2. Significant COSY, HMBC and NOESY correlations of 1–6.

Fig. 3. The plausible biosynthetic mechanism of new lignans 2–5.

Fig. 4. Cinnamophilin (7) reduced the glutamate-stimulated neuronal death in the concentration-dependent manner. PI uptake in cell culture was shown. (A) Primary cortical neurons treated DMSO 20 min then replaced with fresh medium as control. (B) Primary cortical neurons treated DMSO, (C) 1, (D) 3, (E) 10 μM 7 and (F) 20 μM MK-801, after 20 min added 300 μM glutamate for 6 h, n = 6.

Fig. 5. Cinnamophilin (7) reduced the glutamate-stimulated neuronal death in the concentration-dependent manner. Trypan blue uptake in cell culture was shown. (A) Primary cortical neurons treated DMSO 20 min then replaced with fresh medium as control. (B) Primary cortical neurons treated DMSO, (C) 1, (D) 3, (E) 10 μM 7 and (F) 20 μM MK-801, after 20 min added 300 μM glutamate for 6 h, n = 4.

Fig. 6. Cinnamophilin (7) reduced the glutamate-stimulated neuronal death in the concentration-dependent manner. Trypan blue in cell released out by treating 1% Triton X-100 and measured the absorbance at 600 nm. Data are expressed as percentage of control optical density (OD) values. Bars represent the mean ± SD, n = 4. *Significantly different from activated control cultures (one-way ANOVA followed by LSD test, P < 0.05).

Fig. 7. Cinnamophilin (7) reduced the glutamate-stimulated neuronal death in the concentration-dependent manner. After primary cortical neurons in culture were treated 7 (1, 3 and 10 μM) or MK-801 (20 μM) and all were exposed to glutamate (300 μM), culture medium was removed and then sampled for LDH by measuring the absorbance at 490 nm. Data are expressed as percentage of control optical density (OD) values. Bars represent the mean ± SD, n = 6. *Significantly different from activated control cultures (one-way ANOVA followed by LSD test, P < 0.05).