Antiparasitic efficacy of geraniol from Apiaceae family in scabies treatment

Abstract

Sarcoptic mange, commonly known as scabies, is a highly contagious skin condition caused by the burrowing mite Sarcoptes scabiei (Astigmata: Sarcoptinae). This parasitic disease significantly impacts livestock and human health, particularly in underserved regions. Current treatments rely on synthetic acaricides like permethrin and ivermectin, which suffer from limitations such as toxicity, resistance development, and environmental contamination. Essential oils from Apiaceae plants represent a promising natural alternative. This study reviewed 122 volatile constituents from Apiaceae plants and conducted comprehensive in silico analyses to identify potential antiparasitic agents. Geraniol emerged as a potent acaricidal candidate due to its strong binding affinity to acetylcholinesterase (AChE) (docking score: - 7.85 kcal/mol). In vitro testing revealed geraniol achieved a 100% mite mortality rate at concentrations as low as 6.25% within 15 min (LT₅₀ = 9.5 min). In vivo studies using scabies-infected rabbits demonstrated that geraniol-treated animals exhibited complete clinical recovery by two weeks post-treatment, with disappearance of crusts, itching, and skin thickening. Histopathological examination showed near-complete skin regeneration with minimal inflammatory infiltrates, in contrast to control groups which exhibited severe lesions and active mite presence. Furthermore, geraniol-treated rabbits displayed new hair growth and improved general condition, with no observed adverse effects. These findings highlight geraniol's potential as a safe, effective, and eco-friendly treatment for scabies, offering a 100% improvement in clinical and histological recovery within two weeks. Further research should focus on optimizing delivery systems and evaluating its efficacy in human clinical trials.

Keywords: Acaricidal activity; Acetylcholinesterase; Apiaceae; Geraniol; In silico analysis.

Fig. 1

Chemistry of the investigated 122 volatile components identified from members of the Apiaceae family.

Fig. 2

Percentage of the different chemical classes of the selected terpene compounds.

Fig. 3

Different antiparasitic activities of the investigated compounds.

Fig. 4

PCA of the Pa scores of the collected terpenes in this review. Black-colored dots represent structures that got scores < 0.5. Orange-colored dots represent structures with scores between 0.5 and 0.6 against one or two parasites. Blue-colored dots represent structures that got scores between 0.5 and 0.6 against three parasites. Green-colored dots represent structures that have scores between 0.5 and 0.6 or higher against more than three parasites.

Fig. 5

The structures of the top-scoring compounds that were predicted to have antiparasitic activity. Green-colored structures got Pa scores between 0.5 and 0.6 or higher against more than three parasites. Blue-colored structures showed scores between 0.5 and 0.6 against three parasites. Orange-colored structures exhibited scores between 0.5 and 0.6 against one or two parasites.

Fig. 6

Binding modes of geraniol alongside the co-crystallized inhibitor (tacrine) inside the active site of AChE (PDB ID: 6XYY; A,B). RMSDs of geraniol, in comparison with tacrine over a 100-ns long MD simulation (C).

Fig. 7

Survival curves of Sarcoptes scabiei mites exposed to different geraniol concentrations.

Fig. 8

A Rabbit infested with Sarcoptes scabeii mite (from the positive control group) showing severe crust formation in the face and recumbency (A); a rabbit from the treated group, showing normal behavior and disappearance of crusts from the nose and the face (B).

Fig. 9

The progressive curative changes in the nose (A) and external ear (B) of a New Zealand albino rabbit infested with concurrent Sarcoptes scabeii mite after treatment with geraniol (6.25%).

Fig. 10

Photomicrographs stained with H&E, showing the histopathology of the ear tissue in white New Zealand rabbits (2 weeks post-treatment). (A) Normal appearance of the ear tissue in the rabbit of the − ve control group. (B) Regeneration of the epidermal layer, nearly normal dermis, degenerated parasite remnant within the adnexa, slight dermal edema, well-developed fibrous tissue with minimal inflammatory cell infiltration, and mild hyperemia in the geraniol-treated group. (C,D): Hyperkeratosis (arrow), marked acanthosis with formation of rete ridges, hemorrhage, diffuse inflammatory cells infiltration (neutrophils and eosinophils) throughout the dermis, scabs, presence of mites (chevrons) burrowing the epidermis, and sloughed necrotic epithelial debris on tissue surface (star*) in the + ve control and ivermectin-treated group.