Elsevier

Industrial Crops and Products

Volume 158, 15 December 2020, 112951
Industrial Crops and Products

Bioactive compounds from Tunisian Pelargonium graveolens (L’Hér.) essential oils and extracts: α-amylase and acethylcholinesterase inhibitory and antioxidant, antibacterial and phytotoxic activities

https://doi.org/10.1016/j.indcrop.2020.112951Get rights and content

Highlights

  • Forty-two volatile components were identified by GC-FID and GC–MS analyses for P. graveolens essential oil.

  • A significant variation of the phenolic contents attributed to organs was revealed.

  • The highest amounts of polyphenol, flavonoid, flavonol and tannin were shown by the methanolic extracts.

  • Extracts and oils exhibited a strong acethylcholinesterase and α-amylase inhibitory activity.

  • The oils and extracts were found to posses strong antioxidant, antibacterial and phytotoxic activities.

Abstract

The phytochemical composition of Pelargonium graveolens L’Hér. essential oils and extracts of flowers and leaves and their anticholinesterase, anti-α-amylase, antioxidant, antibacterial and allelopathic potential were investigated. Forty-two volatile components were identified by GC-FID and GC–MS analyses. Citronellol (26.98 %–24.3 %), geraniol (20.65 %–21.81 %) and 10-epi-γ-eudesmol (13.06 %–5.13 %) were the main constituents for leaves and flowers oils. The highest amounts of polyphenols (142.71 mg GAE/g DW), flavonoids (52.32 mg RE/g DW) and flavonols (20.15 mg RE/g DW) were shown by the polar subfraction of the leaf extracts. Flowers were characterized by high levels of condensed tannins (13.27 mg CE/g DW). Essential oils and extracts were found to possess important capacity to inhibit the α-amylase and acethylcholinesterase activities. The oils' and extracts antioxidant activity was relatively high, determined by DPPH (IC50 = 711–1280 μg/mL for oils and 12.24–44.24 μg/mL for extracts) and ABTS (15.8–17.95 μg TE/mg DW for oils and 131.54–241.83 μg TE/mg DW for extracts) assays, which was correlated to their phenolic contents. Based on the determination of the diameter of inhibition and the minimum inhibitory concentration, a high antibacterial activity according to oils and extracts was revealed against eleven bacteria strains. Also, the P. graveolens oils and extracts inhibited the shoot and root growth of Medicago sativa L., Triticum aestivum L. and Lactuca sativa L. seedlings. Therefore, P. graveolens can be used as a natural source of bioactive compounds in food and pharmaceutical industries.

Introduction

Pelargonium genus (Geraniaceae) is aromatic plant cultivated for its essential oil which is one of the top 20 essential oils in the world (Ćavar and Maksimović, 2012). It is known for its pharmacological properties in treating bronchitis, fever, diarrhea, cough, gastroenteritis and other respiratory-related ailments (Tahan and Yaman, 2013; Tajkarimi et al., 2010). Also, Pelargonium essential oils were well known for their antifungal, antimicrobial, anti-inflammatory and spasmolytic properties (Boukhatem et al., 2013; Moyo and Staden, 2014). Extracts from roots were also the main ingredient in a remedy used to treat tuberculosis and malaria (Saraswathi et al., 2011). Moreover, others findings suggested that the pharmacological activity of Pelargonium species is partly attributed to their richness in bioactive phytochemicals including oxygenated coumarins, gallic acid-derivatives, flavonoids, phenolic and hydroxycinnamic acid-derivatives (Colling et al., 2010).

The genus Pelargonium is a typical plant with the Mediterranean region and it is consists of ornamental plant. In Tunisia, the most frequent species is P. graveolens popularly known as rose-scented geranium. It exhibits propagation trough vegetative pathway due to its high degree of male and female sterility (Kubba and Tilney-Basset, 1981). It's widely used fresh or dried, as a culinary herb by local communities. In recent years, effective reports on the essential oils composition from areal parts of P. graveolens and their biological proprieties such as antioxidant activity and DNA damage protective have been published (Boukhris et al., 2015; Ćavar and Maksimović, 2012). These authors found that the essential oils composition was dominated by oxygenated monoterpenes with high amounts of citronellol and geraniol, at different phonological stages. Whereas, there is no previous report on the α-amylase and acethylcholinesterase inhibitory and the phytotoxic activity of essential oils and extracts from different plant parts of Tunisian P. graveolens.

Nowadays, medicinal plants are intensely screened and applied in the fields of pharmacology, medical and clinical microbiology, due to their potential as a source of natural biologically active compounds (Derwich et al., 2010). Among various kinds of natural substances, plant secondary metabolites such as essential oils and phenolic compounds are an object of special interest due to their pronounced antioxidant potential. The antioxidants obtained from plants are of greater benefit in comparison to synthetic ones which were found to have undesirable secondary effects on consumer's health (Canadanovic-Brunet et al., 2006). For this reason, the development and utilization of more effective antioxidants of natural origin obtained from botanical sources are desired in preventive medicine and in the food industry because of their interest in the protection of the organism from oxidative stress and for the management of various diseases (Ayaz et al., 2017; Canadanovic-Brunet et al., 2006; Moyo and Van Staden, 2014).

The aim of the present report was (i) to analyze the essential oils and phenolic composition from leaves and flowers of P. graveolens, (ii) to assess the antioxidant, antibacterial and phytotoxic activities of all studied samples and (iii) to investigate their acetylcholinesterase and α-amylase inhibitory activities, in an attempt to contribute to the use of these plant parts as starting material to develop industrial and medicinal uses.

Section snippets

Plant material

Pelargonium graveolens, cultivated in the region of Beja from the North West of Tunisia (Latitude: 36°31′N and Longitude: 8°56′N), was gathered in 2017 at the flowering period during April. According to Emberger’s pluviothermic coefficient Q2 (Emberger, 1966), this region is characterized by its upper semi-arid bioclimate to mild winter with a rainfall of 400–500 mm during the year 2017. The starting material consists of mature plants (0.6–1.1 m). From each plant branches were collected and

Yields and chemical composition of essential oils

The hydrodistillation of P. graveolens aerial parts generated pale yellow colored essential oils with rose scent odor. The yields, based on dry weight, vary between leaves (0.15 %) and flowers (0.18 %). Qualitative and quantitative differences among the essential oils composition extracted from different tissues were revealed (Table 1). In the leaf oils, 31 compounds were identified accounting for 98.86 % of the total oil composition. The major components were citronellol (26.98 %), geraniol

Conclusions

Our analysis on Tunisian P. graveolens showed a high variation in essential oils composition and phenolic contents among organs. It also revealed that extracts and oils have high antioxidant capacities, which suggests that they should be considered as a natural source for beneficial and healthy food. Also, Tunisian P. graveolens possessed an important inhibitory effect against α-amylase and AChE, key enzymes linked to type-2 diabetes and Alzheimer’s diseases. Furthermore, P. graveolens plant

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgments

The authors express their gratitude to the Ministry of Higher Education and Scientific Research, the National Institute of Applied Science and Technology of Tunis and the Higher Institute of Biotechnology of Beja.

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