Comparative Study Regarding the Chemical Composition and Biological Activity of Pine (Pinus nigra and P. sylvestris) Bark Extracts.

Adrian Nisca,Anca Delia Mare,Diana Ionela Stegăruș,Ruxandra Ștefănescu,Corneliu Tanase,Lenard Farczadi

doi:10.3390/antiox10020327

Abstract

The bark resulted after the industrial processing of wood represents a byproduct of the forestry industry, used in many suboptimal ways, being considered a natural waste. Currently, it has been highlighted that the bark of different woody plants may be an important source of several bioactive compounds, with various beneficial biological functions. The aim of this study is to evaluate and compare the chemical composition and biological activities of two different pine species (Pinus nigra and Pinus sylvestris) bark extracts. Ultrasound (UAE) and microwave (MAE) assisted extractions were performed in order to obtain the extracts. The total polyphenol (TPC) and total tannin (TTC) contents of the extracts were assessed via the Folin–Ciocâlteu method. The volatile and polyphenolic compounds were identified and quantified via a GC/MS analysis and an UPLC-PDA analysis, respectively. The antioxidant activity (AOA) was evaluated using the DPPH and ABTS assays, while the antibacterial activity was assessed using the minimum inhibitory concentration (MIC) protocol. The results showed that the Pinus sylvestris bark extracts obtained by UAE had a higher TPC, TTC and AOA, while the Pinus nigra bark extracts obtained by MAE had higher volatile compounds content (mainly α-pinene and β-pinene). Moreover, the inhibition of the bacterial growth was more efficient in the case of Pinus sylvestris extracts, Gram-positive bacteria being the most affected, while Gram-negative strains presented a relative resistance to the tested extract concentrations. These results may indicate the potential use of the pine bark extracts as antioxidant or antibacterial agents.

Highlights

In present days, the attention of researchers in the field is drawn towards the discovery of new bioactive compounds, which may be used for various purposes
Taking into account all the results of the present study, it can be concluded that major differences may occur between the chemical compositions and biological effects of the tested pine species, and between the two extraction methods used
It could be noted that the P. sylvestris extracts acquired by ultrasound assisted extraction (UAE), presented the highest content of polyphenolic compounds and tannins, while the P. nigra variant acquired by MAE, had the biggest amount of α-pinene and β-pinene for the parameters set in the present study

Summary

Introduction

The attention of researchers in the field is drawn towards the discovery of new bioactive compounds, which may be used for various purposes. The main sources of phenolic compounds are fruits and vegetables, more recent studies have shown that the bark of woody vascular plants may represent a major source of phenolics [1,3] Their role as protective agents against different plant pathogens might explain why these compounds are found in the bark of different species [3,4,5,6]. The effects of these compounds on human health are intensely studied and most often linked to their antioxidant activity. Antimycotic effects against different species of the Candida, Penicillium and Aspergillus [16,17,18], and antiviral activities against HIV and Herpes simplex [19,20,21] were highlighted in studies regarding phenolic compounds

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