Supercritical CO₂ extraction of Aloysia gratissima leaves and evaluation of anti-inflammatory activity

Highlights

• The temperature and the pressure influenced in the extraction process.

• There was an increase of yield when high temperature and pressure were combined.

• The major compounds were guaiol and pinocanphone.

• Spathulenol, β-elemene, cariophyllene and cariophyllene oxide contribute to the anti-inflammatory activity.

Abstract

This work aims to evaluate the effects of temperature and pressure on the extraction yield and chemical composition of the supercritical CO₂ (SCCO₂) extracts of A. gratissima leaves (EAG) and then to investigate in vivo anti-inflammatory activity of the extracts. The leaves of A. gratissima were extracted with supercritical CO₂ at 40, 50 and 60 °C and 15, 17.5 and 20 MPa for 120 min. The anti-inflammatory activity was performed with the EAG obtained at 60 °C and 20 MPa. The anti-inflammatory activity was investigated by the carrageenan-induced paw edema and myeloperoxidase (MPO) activity in paw tissue. The chemical analysis showed the presence of guaiol, pinocamphone, caryophyllene oxide and spathulenol as the major chemical components of the EAG. These compounds may have contributed to the significant reduction of carrageenan-induced paw edema and MPO activity in the first 3 h after the injury induction.

Introduction

The species belonging to the Verbanecea family have hydrocarbon compounds, of which more than half are sesquiterpenes [1]. Among the plants belonging to this family, it can be highlighted Aloysia gratissima, a native aromatic plant from southern Brazil [2]. Aloysia gratissima is known in folk medicine, being studied for viricidal [3], nematicide [4], antioxidant [5], antidepressant, neuroprotective [2], antibacterial and antiedematogenic [6] activities. There are no reports of anti-inflammatory activity for this plant in the scientific literature.

Inflammation is a reaction of the body to infection or tissue damage. According to Trevisan et al., [7], inflammation is an important defense mechanism of the host, being characterized by redness, swelling, pain, heat and dysfunction of tissues and organs. Non-steroidal anti-inflammatory drugs (NSAIDs) are first-line drugs used to reduce the harmful events associated with inflammation. The disadvantages of the use of NSAIDs, such as the high risk of gastrointestinal mucosal damage, ulcers and erosions, kidney damage, increased blood pressure and heart diseases [8,9] can be minimized when they are replaced with efficient medicinal plants derived compounds [10]. The use of plants with anti-inflammatory properties received most interest today. In Brazil, medicinal plants play an important role in public health, and the Ministry of Health has released a list of medicinal plants with anti-inflammatory activity [11]. Regarding the therapeutic potential against inflammatory’ diseases, several species of aromatic plants rich in mono and diterpenes have shown important results, such as Origanum vulgare [12], and thymus vulgaris [13]. among others [14,15]. Previous studies have shown that the Aloysia gratissima plant is rich in mono and diterpenes [16] which demonstrates possible anti-inflammatory properties.

In the study of medicinal plants, the elaboration of the extracts is one of the most important phases. Supercritical fluid extraction appears as an alternative method of extraction compared to conventional techniques such as steam distillation or Soxhlet extraction, because it avoids solute contamination with solvent residues and the degradation of thermo sensitive compounds [17] Carbon dioxide is the most commonly used solvent for supercritical extraction due to its favorable properties [18]. Supercritical CO₂ produces high-quality extracts rich in terpenes from plant material with anti-inflammatory activity of properties [12]. In this sense, the objective of this work was to investigate the anti-inflammatory activity of A. gratissima leaves extract obtained by supercritical CO₂ (SCCO₂) under conditions that presented the highest extraction yield and the identification of the chemical components present in the extract.