Plant volatile organic compounds (volatiles) are secondary plant metabolites that play crucial roles in the reproduction, defence, and interactions with other vegetation. They have been shown to exhibit a broad range of biological properties and have been investigated for antimicrobial and anticancer activities. In addition, they are thought be more environmentally friendly than many other synthetic chemicals 1. Despite these facts, their applications in the medical, food, and agricultural fields are considerably restricted due to their volatilities, instabilities, and aqueous insolubilities. Nanoparticle encapsulation of plant volatile organic compounds is regarded as one of the best strategies that could lead to the enhancement of the bioavailability and biological activity of the volatile compounds by overcoming their physical limitations and promoting their controlled release and cellular absorption. In this review, we will discuss the biosynthesis and analysis of plant volatile organic compounds, their biological activities, and limitations. Furthermore, different types of nanoparticle platforms used to encapsulate the volatiles and the biological efficacies of nanoencapsulated volatile organic compounds will be covered.

Rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma in paediatric patients. Relapsed or refractory RMS shows very low 5-year survival rates, which urgently necessitates new chemotherapy agents. Herein, the sesquiterpene lactone, helenalin, was investigated as a new potential therapeutic agent against the embryonal RMS (eRMS) and alveolar RMS (aRMS) cells. We have evaluated in vitro antiproliferative efficacy of helenalin on RMS cells by the MTT and wound healing assay, and estimated several cell death pathways by flow cytometry, confocal microscopy and immunoblotting. It was shown that helenalin was able to increase reactive oxygen species levels, decrease mitochondrial membrane potential, trigger endoplasmic reticulum stress and deactivate the NF-κB pathway. Confirmation was obtained through the use of antagonistic compounds which alleviated the effects of helenalin in the corresponding pathways. Our findings demonstrate that oxidative stress is the pivotal mechanism of action of helenalin in promoting RMS cell death in vitro.

Confining chemotherapy to tumour sites by means of active targeting nanoparticles (NPs) may increase the treatment effectuality while reducing potential side effects. Cubosomes are one of the next-generation drug delivery nanocarriers by virtue of their biocompatibility and bioadhesion, sizeable payload encapsulation and high thermostability. Herein, an active tumour targeting system towards rhabdomyosarcoma (RMS) cells was evaluated. Cubosomes were loaded with helenalin (a secondary metabolite from Arnica plants), which we have previously shown to induce apoptosis in RMS cells. The functionalization of the cubosomes was accomplished to enable binding to membrane receptors and translocation under a magnetic field. RMS cells overexpress CD44 and CD221 on their membrane surface and, therefore, hyaluronic acid (HA, a ligand for CD44) and antibodies (Abs) against CD221 were coupled to cubosomes via electrostatic attraction and the thiol-Michael reaction, respectively. Magnetization of the cubic phase NPs was achieved by embedding superparamagnetic iron oxide NPs (SPIONPs) into the cubic matrix. Single-function and multi-function cubosomes had Im3m cubic phase structures with well-organized lattice patterns. Conjugation with 2% HA or anti-CD221 half Abs and/or 1% SPIONPs showed significantly higher uptake into RMS cells compared to unfunctionalized cubosomes. CD44 and CD221 directed magnetic (triple-function) cubosomes were capable of internalizing into RMS cells in an energy-independent mechanism. Helenalin-laden triple functionalized cubosomes showed limited impact on the viability of control fibroblast cells, while they induced a high degree cytotoxicity against RMS cells. Profound tumour cell death was observed in both two-dimensional (2D) culture and three-dimensional (3D) tumour spheroids.