*2.1. HPLC Analysis*

Phytochemical profiling of *A. lackoocha heartwood* was carried out by HPLC. Each extract was investigated (water, ethanol and ethyl acetate) and found to contain one single dominant peak with a retention time consistent with that of the chromatogramic standard of oxyresveratrol (Figure 2A). The chromatographic standard of resveratrol was also used allowing accurate calculation of the amounts of each compound in each extract (Figure 2B). Further authentication of the predominant peak was carried out using NMR with the 13C-NMR and 1H-NMR; the chemical shifts and structure elucidated in Figure 3. were in good agreement with the standard. Mass spectra of the main peak detected at RT 14.0 supposed to be oxyresveratrol showed the spectra patterns were the same as the standard (showed in the Supplementary Materials). Its molecular formula C14H12O4 was deduced from the ESI-MS spectrum in positive ion mode by the hydriated molecular ion peak at *m*/*z* 245 [M + H]+. The amount of oxyresveratrol in the plant was consistent with the range reported by Maneechai et al. [3], while the amount of resveratrol was lower compared to the report from Borah et al. [4].

**(A)** 

**Figure 2.** *Cont.*


**Figure 2.** Chemical profiles and contents of oxyresveratrol and resveratrol in *A. lakoocha* heartwood extracts. (**A**) Chemical profiles of the compounds in the extracts at 250 μg/mL were analysed by HPLC at a wavelength of 320 nm; water extract, ethanol extract, ethyl acetate extract, and standard oxyresveratrol and resveratrol at 10 μg/mL. (**B**) Amount of oxyresveratrol and resveratrol detected in *A. lakoocha* heartwood extracts.

**(B)** 


**Figure 3.** 13C-NMR (300 MHz, Acetone-d6) and 1H-NMR (300 MHz, Acetone-d6) data of oxyresveratrol.

#### *2.2. DNA Nicking Assay*

The ability of oxyresveratrol to cause DNA damage in the presence of 50 μM copper(II) was investigated (Figure 4A). Oxyresveratrol was consequently found to cause double-strand breaks in supercoiled plasmid DNA in a dose-dependent manner (lane 5–10); 200 μM was the most effective at inducing this DNA damage, while no DNA damage was found at low oxyresveratrol concentrations (0.4–2 μM). The DNA damaging activity of oxyresveratrol was found to be dependent on the presence of Cu(II) ions, and not Fe(II) or Zn(II)(data not shown). Comparison of the DNA-damaging capacity of equivalent concentrations (50 μM) of stilbene derivatives revealed only DNA damage being induced by oxyresveratrol and resveratrol (Figure 4B), of which oxyresveratrol was the most damaging. The DNA-damaging capacity of a series of hydrostilbenoids was previously investigated and in contrast to the data reported here resveratrol was found to be the most active [6]. The DNA-damaging capacity was specifically induced by copper ions, one of the most abundant metal ions in biological systems [12]. This raises the possibility that the DNA damage observed may be due to ROS generation

via the Fenton reaction consistent previous observations made by Moran et al. [13] who observed similar findings with a number of other phenolic compounds.
