**3. Materials and Methods**

#### *3.1. Preparation of PN from the Seeds of Pharbitis nil*

PN was prepared as previously reported [34]. In brief, dried seeds of *Pharbitis nil* (1 kg) were ground. Then, ground *Pharbitis nil* was immersed in methanol (MeOH) at room temperature for 48 h and extracted. The MeOH extract was filtered with 5 μm filter paper and concentrated using a rotary evaporator (Tokyo Rikakikai, Tokyo, Japan). To purify compound PN, the MeOH extract (5 g) was dissolved in 50% MeOH and chromatographed on a Diaion HP-20 column by the gradient MEOH (50%, 80%, 100%, each fraction 500 mL). The 100% MeOH fraction (800 mg) was further chromatographed on reversed-phase C-18 and Sephadex LH-20 column using 100% MeOH as mobile phase, simultaneously. The 250 mg of purified compound PN was confirmed by high performance liquid chromatography (HPLC) in our previous study.
