Isolation of Lignans from Magnolia grandiflora

Mature seeds of M. grandiflora were collected at the University of Mississippi (MS 38,677) in November 2013. The voucher specimen (NCNPR #15,895) is deposited at the University of Mississippi. The air-dried seeds (107 g) were powdered and extracted with n-hexane (200 mL × 2 for 24 h) followed by 95% EtOH. The combined hexane extracts were evaporated under reduced pressure. Two grams of hexane extract were chromatographed over a centrifugal preparative thin layer chromatographer (CPTLC, Chromatotron^®, Analtech Inc., Newark, DE, USA) using a 6 mm silica gel rotor. The sample was dissolved in dichloromethane (DCM), applied to the rotor, and then eluted with n-hexane, followed by DCM and MeOH (200 mL each) to yield eighteen fractions. These fractions later yielded three major lignans, 4-O-methylhonokiol (1, 36 mg), honokiol (2, 20 mg), and magnolol (3, 15 mg), together with marked fatty acids. All fractions were monitored and collected via TLC analysis (silica gel; solvents: n-hexane-EtOAc; 75:25).
4-O-methylhonokiol (1); UPHPLC/APCI-MS m/z 281.3 ([M + H])⁺ C₁₉H₂₀O₂ + H; the ¹H and ¹³C NMR were indistinguishable to those reported [34 (link)].
Honokiol (2); UPHPLC/APCI-MS m/z 267.3 ([M + H])⁺ C₁₈H₁₈O₂ + H; the ¹H and ¹³C NMR were indistinguishable to those reported [35 (link)].
Magnolol (3); UPHPLC/APCI-MS m/z 267.3 ([M + H])⁺ C₁₈H₁₈O₂ + H; the ¹H and ¹³C NMR were indistinguishable to those reported [35 (link)].