Lavender leaves extract biocompatibility
Lavandula genus plants have been widely used in traditional medicine due to their high content of bioactive compounds
(Oueslati et al., 2020). Those bioactive compounds include monoterpenes, polyphenols and sesquiterpenes
(Areias et al., 2000). Those constituents give lavender various properties such as antiseptic, anti-inflammatory, analgesic, antioxidant, antimicrobial and antifungal activities
(Chrysargyris et al., 2016; El Abdali et al., 2022). Therefore, extracts of lavender have been used in the food, perfume and cosmetics industries
(Wells et al., 2018). In the present study, we aimed to evaluate the biological properties of
L. dentata L. leaves extract (LE) that are collected in Saudi Arabia, Taif region.
In the cell viability assay on human skin fibroblast (HSF), Figure 2A shows a high cytotoxic effect of Cisplatin (positive control, 0.001-100 mg/mL) in a dose-dependent manner with IC
50 = 0.78 mg/mL, while LE appears to be safer on the same cell line. LE at concentrations of 0.01, 0.1, 1, 100 and 1000 mg/ml decreased cell viability dose-dependently with IC
50 = 97 mg/mL (Figure 2B). Our data indicate that LE has low cytotoxicity
in vitro at low concentrations, which agrees with
Cardia et al., (2018). They have reported mice leukocytes viability>75% up to a concentration of 10 mg/mL of
L. angustifolia oil (LAO) using MTT Assay. However, LAO at higher concentrations (30 and 90 mg/ml) affected cell viability. They concluded that LEO has a cytotoxicity dose-dependent manner and can vary with its constituents
(Prashar et al., 2004). In addition,
Alnamer et al., (2012) have reported the non-toxic potential of
L. officinalis extract as an oral administration.
L. dentata’s low cytotoxicity could be attributed to its antioxidant potential. Moroccan
L. dentata oil consists of 16 constituents with the major component being linalool (45.06%), then camphor (15.62%) and borneol (8.28%) making it an effective natural agent against free radical damage (
El Abdali et al., 2022).
Wound healing assay
The skin represents the largest organ in the body that acts as a biological barrier against injuries, burns, illness and any external stress
(Mssillou et al., 2022). A wound is a tissue injury because of several chronic diseases including diabetes, trauma and cancer, which are among the major clinical problems
(Shrivastav et al., 2018; Valente et al., 2019). Worldwide, 6 million people are suffering from non-healing wounds (85% of aged persons) resulting in enormous healthcare expenditures (
Paladini and Pollini, 2019). The recovery period of a wound might take a few days in healthy people, which is prolonged in acute, while impaired in chronic wounds
(Yadav et al., 2021). The wound healing process includes four phases: hemostasis, inflammation, proliferation and remodeling
(Belachew et al., 2020). Several medicinal plants have been proven to increase the renewal rate of damaged tissues
in vivo,
in vitro and in excisional and incisional experimental models such as
Nepeta dschuparensis,
Chamaecostus cuspidatus,
Nigella sativa,
Aristolochia saccate and others
(Bolla et al., 2019; Low et al., 2021; Naeimi et al., 2020; Ponnanikajamideen et al., 2019; Sallehuddin et al., 2020).
We have chosen one of the commonly used medicinal plants that are cultivated in KSA and used in numerous therapies,
Lavandula dentata. Saudi Arabia has a diverse flora comprising different species that include numerous medicinal plants due to its vast area of diverse geographical landscapes and climates. Therefore, ethnomedical native plants are traditionally used in KSA for therapy, including wound healing
Aati et al., (2019). According to Fig 3 (A-E), several parameters are measured to determine the wound-healing potential of LE methanolic extract (a quarter of IC
50=24.24 mg/mL) at 0, 24h, 48h, 72h and 96 interval time. We have chosen ¼ of IC
50 as a safe dose for LE treatment to prevent cell death (HSF cells) at higher doses. We have determined that LE decreased wound width (Fig 4A) and wound area (Fig 4B) in a time-dependent manner (0, 24h, 48h, 72h and 96h) in comparison to negative control. In addition, LE (24.24 mg/mL) decreased the mean cell migratory rate of wound border cells during scratch closure (Fig 4C) and increased the wound closure % (Fig 4D). However, for all parameters of the wound healing assay, there is a non-significant difference between LE treatment and the negative control group at different interval times. This could be returned to the selected very low dose of LE treatment for skin fibroblast cells. From a long time ago until now, different plants have been used in wound healing as a traditional medicine in KSA regions such as leaves and whole plant
of Blepharons ciliaris L., leaves of
Ecbolium gymnostachyum, leaves of
Hypoestes forsskalii, whole plant of
Euryops arabicus Steud (
Al-Sodany et al., 2013),
Adenium arabicum Balf, leaves of
Centaurothamnus maximus, leaves of
Verbesina encelioides, leaves and seeds of
Diplotaxis acris (Forssk) Boiss (
El-Shabasy, 2016), fruits of
Tamarindus indica L.
(Aly et al., 2022) and others
(Aati et al., 2019).
Leaves and flowers of
Lavandula dentata L. have been used for headache, relieve rheumatic pain and cold
(Al-Sodany et al., 2013) but in our peer knowledge, it is the first time to assess the wound healing potential of
Lavandula dentata cultivated in KSA
. It was reported that
L. dentata extracts consist of many compounds, but the major constituents are linalool, camphor and borneol which belong to oxygenated monoterpenes, b-farnesene which belongs to Sesquiterpene hydrocarbons and 1,8 cineole. It was reported that the concentration of LE constituents differs from one cultivated region to another such as in eastern Morocco
(Imelouane et al., 2009), Moroccan middle Atlas
(Soro et al., 2014), Brazil
(Justus et al., 2018) and Italy
(Giuliani et al., 2020). The chemical composition of LE varied depending on the mplant part (roots, leaves and flowers) from which it was extracted, geographical origins, seasonal changes, harvest time, genetic variability and growth conditions
(Bouyahya et al., 2023). Natural compounds present in medicinal plants can accelerate the wound healing process by promoting epithelization
(Farzaei et al., 2015), increasing vasculogenesis and angiogenesis (
Caban and Lewandowska, 2021) and modulating the inflammatory cytokines
(Hu et al., 2011) and finally enhancing wound contraction rates
(Yin et al., 2015).
Antimicrobial potential of LE
Four different bacterial strains were selected because they are common in wound infections:
E. coli,
S. aureus,
P. aeruginosa and
S. pyogenes (
Puca et al., 2021). Antimicrobial resistance is considered a top ten threat to global health according to the World Health Organization (
WHO, 2019). This resistance returns to the inappropriate use of antimicrobial drugs in humans and the unpleasant appearance of multi-drug resistant strains, which represents a public health concern. The WHO report indicates high annual deaths due to multi-drug resistant pathogens in Europe (25,000 deaths/year) and the United States (23,000 deaths/year). In addition, about 50% of infections are associated with
K. pneumoniae,
E. coli,
S. aureus and
P. aeruginosa (Pallavali et al., 2017; WHO, 2014). Therefore, the present study has been established for the antimicrobial assessment of the methanolic extract of LE.
Fig 5 and Table 1 show the antibacterial potential of LE against aerobic bacterial strains that infect wounds: Gram-negative (
E. coli and
P. aeruginosa) and Gram-positive (
S. aureus and
S. pyogenes). Table 1 shows that LE has a higher antimicrobial effect against all four strains at MIC and MBC> 3.0 mg/mL, except for
Streptococcus pyogenes MIC
= 3.0 mg/mL. However, ciprofloxacin has a higher antimicrobial effect at MIC<0.005 mg/mL. In agreement with our results,
El-Said et al., (2021) in Saudi Arabia tested essential oil extracted from flowering aerial parts of
L. pubescens against 13 strains of Gram-negative and Gram-positive bacteria using the agar diffusion assay. Their results revealed that LE had antimicrobial potential, but Gram-negative strains were more susceptible than Gram-positive ones. In addition,
Hossain et al., (2017) tested the flowering part of
L. angustifolia in Bulgaria against various pathogenic bacteria isolated from pet turtles belonging to seven species:
Aeromonas hydrophila,
Aeromonas caviae,
Citrobacter freundii,
Proteus mirabilis,
Salmonella enterica, Aeromonas dhakensis and
Ps. aeruginosa. Their results reported the LE antibacterial effect against all tested strains except
Ps. aeruginosa.
The major chemical constituents of the LE (linalool, linalyl acetate and terpinen-4-ol) are responsible for the antimicrobial effect. These components damage the lipid layer of the cell membrane, which results in bacterial cell leakage and death (
De Rapper et al., 2016). Recently, it has been reported that lavender essential oil induces oxidative stress on bacterial cells, disrupts their membrane and then dies through proteomic and genomic analyses
(Yang et al., 2020, Yang et al., 2021). Further study is needed to report the specific mode of action of LE against bacterial strains.
