Molecular level comparison of water extractives of maple and oak with negative and positive ion ESI FT-ICR mass spectrometry

Authors: He, Zhongqi; SLEIGHTER, RACHEL - Old Dominion University; HATCHER, PATRICK - Old Dominion University; LIU, SHASHA - Chinese Research Academy Of Environmental Sciences; WU, FENGCHANG - Chinese Research Academy Of Environmental Sciences; ZOU, HAIXUAN - University Of Maine; Olanya, Modesto

Submitted to: Journal of Mass Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2019
Publication Date: 8/1/2019
Citation: He, Z., Sleighter, R.L., Hatcher, P.G., Liu, S., Wu, F., Zou, H., Olanya, O.M. 2019. Molecular level comparison of water extractives of maple and oak with negative and positive ion ESI FT-ICR mass spectrometry. Journal of Mass Spectrometry. 54(8):655-666. https://doi.org/10.1002/jms.4379.
DOI: https://doi.org/10.1002/jms.4379

Interpretive Summary: In previous research, we improve the water resistance of cottonseed meal-based wood adhesives by removing the water soluble components in the cottonseed meal. However, the composition and function of water soluble components of the wood substrates on the bio-based adhesive bonding is unknown. Increased knowledge on the water extractives of wood would be helpful in our understanding of their potential, thus improving the strategies, of wood-adhesive bonding by cottonseed meal. In this work, the chemical composition of the water extractives of maple and oak was compared and characterized by ultraviolet-visible (UV-vis) spectroscopy and positive and negative ion mode ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The resulting data indicated that lignin-, carbohydrate- and tannin-like compounds were the three major categories of the chemicals detected. The top 25 peaks (formulas) accounted for 47.1% and 63.8% of the relative abundance of the maple extractives with the negative and positive ion FT-ICR MS analysis, respectively, and 45.5% and 33.5% of the relative abundance of the oak sample with two ion mode data. The profiles of the top 25 formulas differed between the two wood samples although 4 formulas appeared in the spectra of both samples. Among the 20 formulas of the top 5 peaks of the four spectra, 17 could be assigned to specific bioactive chemical compounds related to tree and other plant biomass, based on the literature comparisons. This knowledge is helpful in the ongoing improvement and mechanism studies of cottonseed meal adhesive-wood bonding interaction. It also provides information for further application of FT-ICR MS for chemical markers useful in profiling and identification of wood types and sources.

Technical Abstract: Soluble extractives in wood function to protect living trees from destructive agents and also contribute to wood color and fragrance. Some extractive components have biological activities with medical applications. They also play important roles in wood processing and related applications. To increase the knowledge of wood chemistry, maple and oak were extracted by water. Ultraviolet/visible (UV/vis) spectroscopy indicated the presence of a phenolic compound resorcinol in maple extractives with higher molecular mass and more aromatic components than oak extractives. Negative and positive electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) identified thousands of formulas in the two samples in the m/z range of 200-800. They mainly fall into the lignin-, carbohydrate- and tannin-like compound categories, Even though, top 25 peaks (formulas) represented about 50% of the relative abundance of the chemicals in maple extractives and about 40% of the chemicals in oak extractives. Indeed, the top one peak accounted for 14% of the abundance in both wood samples with the negative ion mode analysis. Literature comparisons identified 17 of 20 formulas in top 5 peaks of the four spectra as specific bioactive compounds in tree and other plants, implying the potential to explore utilization of maple and oak extractives for functional and medicinal applications. The different profiling of the top 25 peaks from the two samples also suggested the possible application of FT-ICR MS spectrometry for chemical markers useful in profiling and identification of wood types and sources.