Fig. 3

Phenolic compounds in teak (Tectona grandis L. f.): Unidentified compounds are H1 and P1. Identified compounds are tectoquinone, 2-(hydroxymethyl)anthraquinone, anthraquinone-2-carboxylic acid, lapachol, 1,4-naphthoquinone. They are detected at 254 nm in wood samples from the sapwood (SW) and heartwood (HW). Heartwood is divided into outer heartwood (OHW), middle heartwood (MHW), and inner heartwood (IHW). Values are the mean of six separate samples for the sapwood and for the outer, the middle, and the inner heartwood. Standard deviations are displayed as bars. a–g indicate statistically significant values using the Mann–Whitney test when p < 0.05