Promotion of mammalian angiogenesis by neolignans derived from soybean extracellular fluids

The study of the chromatographic behavior and a mass spectrometric approach to differentiating the diastereomer pair of the β-O-4 lignin dimer series

Lignin and lignans are natural products found in plant cell walls. Lignin research has historically focused on lignin degradation techniques in the hope of converting lignin into useful aromatic carbon feedstocks. In contrast, investigations of lignans existing as natural product dimers, have been focused on thier interesting biological activities. Many lignan compounds are chemically identical to dimers derived from lignin, and both lignin and lignan dimers can possess multiple chiral centers leading to observations of diastereomer pairs where one diastereomer exhibits the bulk of the activity. For example, the G-(β-O-4')-G dimer was reported to have a pro-angiogenic activity with one diastereomer of the pair showing enhanced pro-angiogenic activity. Traditional analytical techniques such as nuclear magnetic resonance (NMR) can differentiate the diastereomer pairs of β-O-4 compounds; however, isolation of a pure sample is often required for analysis. This work was aimed at exploring the potential use of tandem mass spectrometry to differentiate diastereomer pairs in the β-O-4 dimer series. Each diastereomer pair in the nine-dimer series was separated by HPLC and interrogated by tandem mass spectrometry. To understand the chromatographic behavior of the diastereomer pair in the β-O-4 dimer series, three commercially available reverse phase HPLC columns were evaluated. A temperature programming experiment using water/acetonitrile isocratic elution showed that the chromatographic retention mechanism of these diastereomers was hydrophobically driven with analytes having more methoxy groups exhibiting larger ΔH⁰ and higher octanol-water partition coefficient values. Tandem mass spectrometry performed on each of the diastereomers produced fragment ions having different ion abundances. A mechanistic study based on the ion abundance of "sequence-specific ions" and "-48 ions" was used to assign a configuration to each of the pairs of diastereomers in the nine-dimer series.

Lignans and Neolignans: Plant secondary metabolites as a reservoir of biologically active substances

Lignans and neolignans are plant secondary metabolites derived from the oxidative coupling of phenylpropanoids. Biological activity of these phenolic compounds ranges from antioxidant, antitumor (terminaloside P, IC₅₀ = 10 nM), anti-inflammatory, anti-neurodegenerative (schibitubin B, IC₅₀ = 3.2 nM) and antiviral (patentiflorin A, IC₅₀ = 14-23 nM) to antimicrobial. In addition, it was observed that several members of this group, namely enterolactone and its biochemical precursors also known as phytoestrogens, possess important protective properties. Most of these lignans and neolignans are presented in reasonable amounts in one's diet and thus the protection they provide against the colon and breast cancer, to name a few, is even more important to note. Similarly, neuroprotective properties were observed (schisanwilsonin G, IC₅₀ = 3.2 nM) These structural motives also serve as an important starting point in the development of anticancer drugs. Presumably the most famous members of this family, etoposide and teniposide, synthetic derivatives of podophyllotoxin, are used in the clinical treatment of lymphocytic leukemia, certain brain tumors, and lung tumors already for nearly 20 years. This review describes 413 lignans and neolignans which have been isolated between 2016 and mid-2018 being reported in more than 300 peer-reviewed articles. It covers their source, structure elucidation, and bioactivity. Within the review, the structure-based overview of compounds as well as the bioactivity-based overview of compounds are described.