1,6-Dehydropinidine Is an Abundant Compound in Picea abies (Pinaceae) Sprouts and 1,6-Dehydropinidine Fraction Shows Antibacterial Activity against Streptococcus equi Subsp. equi.

Virpi Virjamo,Akseli Koskinen,Katri Nissinen,Pia Fyhrquist,Anu Lavola,Riitta Julkunen-Tiitto

doi:10.3390/molecules25194558

Virpi Virjamo, Akseli Koskinen + Show 4 more

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https://doi.org/10.3390/molecules25194558

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Abstract

Knowledge about the defensive chemistry of coniferous trees has increased in recent years regarding a number of alkaloid compounds; in addition to phenolics and terpenes. Here, we show that Norway spruce (Picea abies (L.) H. Karst.), an important boreal zone tree species; accumulates 1,6-dehydropinidine (2-methyl-6-(2-propenyl)-1,6-piperideine) in its needles and bark. We reanalyzed previously published GC-MS data to obtain a full picture of 1,6-dehydropinidine in P. abies. 1,6-dehydropinidine appeared to especially accumulate in developing spring shoots. We used solid-phase partitioning to collect the alkaloid fraction of the sprouts and thin-layer chromatography to purify 1,6-dehydropinidine. The antibacterial properties of the 1,6-dehydropinidine fraction were tested using a broth microdilution method; with Streptococcus equi subsp. equi as a model organism. Based on our results 1,6-dehydropinidine is common in alkaloid extractions from P. abies (0.4 ± 0.03 mg g−1 dw in mature needles) and it is especially abundant in young spruce shoots (2.7 ± 0.5 mg g−1 dw). Moreover; 1,6-dehydropinidine extracted from P. abies sprouts showed mild antibacterial potential against Streptococcus equi subsp. equi (MIC 55 µg mL−1). The antibacterial activity of a plant compound thought of as an intermediate rather than an end-product of biosynthesis calls for more detailed studies regarding the biological function of these coniferous alkaloids

Highlights

Pinus sylvestris L. and Picea abies (L.) H
When concentrations were calculated as epidihydropinidine equivalents, 1,6-dehydropinidine was one of the most abundant piperidine alkaloid compounds in P. abies, accounting for, on average, 42.3% (±1.4 SEM) of total piperidine alkaloid yield
The highest concentration of 1,6-dehydropinidine was detected from P. abies trees with genetic backgrounds in Latvia and the lowest concentration was detected in trees with backgrounds in Northern Finland (Table 2)

Summary

Introduction

Pinus sylvestris L. and Picea abies (L.) H. The wood extractives of these species have shown to have antibacterial properties against methicillin-resistant Staphylococcus aureus and Escherichia coli [2] and P. abies resin-based salve has been proven to be clinically effective for the treatment of chronic wounds [3]. The defensive chemistry of coniferous species consists of all three major secondary chemistry groups—phenolics (e.g., acetophenones, lignans, stilbenes, flavonoids, phenolic acids and proanthocyanidins), terpenes (e.g., monoterpenes and resin acids) and alkaloids (piperidines) but Molecules 2020, 25, 4558; doi:10.3390/molecules25194558 www.mdpi.com/journal/molecules 25, x4558 Molecules. Piperidine alkaloids are traditionally considered more important in assumed to be phenolic and terpene compounds [1]. Piperidine alkaloids are traditionally considered plant-herbivore interactions than in microbial defense [4,5]. The role of alkaloids in microbial more important in plant-herbivore interactions than in microbial defense [4,5]. The role of interactions has, attracted increasing attention (e.g., Reference [6]) which raises the question alkaloids in microbial interactions has, attracted increasing attention (e.g., Reference [6])

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