Niaouli Research Articles

Inhibition of Escherichia Virus MS2, Surrogate of SARS-CoV-2, via Essential Oils-Loaded Electrospun Fibrous Mats: Increasing the Multifunctionality of Antivirus Protection Masks.

One of the most important measures implemented to reduce SARS-CoV-2 transmission has been the use of face masks. Yet, most mask options available in the market display a passive action against the virus, not actively compromising its viability. Here, we propose to overcome this limitation by incorporating antiviral essential oils (EOs) within polycaprolactone (PCL) electrospun fibrous mats to be used as intermediate layers in individual protection masks. Twenty EOs selected based on their antimicrobial nature were examined for the first time against the Escherichia coli MS2 virus (potential surrogate of SARS-CoV-2). The most effective were the lemongrass (LGO), Niaouli (NO) and eucalyptus (ELO) with a virucidal concentration (VC) of 356.0, 365.2 and 586.0 mg/mL, respectively. PCL was processed via electrospinning, generating uniform, beadless fibrous mats. EOs loading was accomplished via two ways: (1) physisorption on pre-existing mats (PCLaEOs), and (2) EOs blending with the polymer solution prior to fiber electrospinning (PCLbEOs). In both cases, 10% v/v VC was used as loading concentration, so the mats’ stickiness and overwhelming smell could be prevented. The EOs presence and release from the mats were confirmed by UV-visible spectroscopy (≈5257–631 µg) and gas chromatography-mass spectrometry evaluations (average of ≈14.3% EOs release over 4 h), respectively. PCLbEOs mats were considered the more mechanically and thermally resilient, with LGO promoting the strongest bonds with PCL (PCLbLGO). On the other hand, PCLaNO and PCLaELO were deemed the least cohesive combinations. Mats modified with the EOs were all identified as superhydrophobic, capable of preventing droplet penetration. Air and water-vapor permeabilities were affected by the mats’ porosity (PCL < PCLaEOs < PCLbEOs), exhibiting a similar tendency of increasing with the increase of porosity. Antimicrobial testing revealed the mats’ ability to retain the virus (preventing infiltration) and to inhibit its action (log reduction averaging 1). The most effective combination against the MS2 viral particles was the PCLbLGO. These mats’ scent was also regarded as the most pleasant during sensory evaluation. Overall, data demonstrated the potential of these EOs-loaded PCL fibrous mats to work as COVID-19 active barriers for individual protection masks.

Evaluation of essential oils as seed treatment for the control of Xanthomonas spp. associated with the bacterial leaf spot of tomato in Tanzania

Bacterial leaf spot (BLS) caused by Xanthomonas spp. is a serious and a major constraint to tomato production worldwide. The seed-borne nature of BLS, the complex nature of the disease, which is caused by different bacterial species and the current ineffective control measures have made the evaluation of alternative control compounds for seed treatment necessary. Therefore, the efficacy of 11 essential oils applied as seed treatments to control Xanthomonas perforans in tomato and the effect on seed germination and seedling growth was evaluated. Seed treatment with oils of eucalyptus (Eucalyptus globules Labill.), rosemary (Rosmarinus officinalis L.) and niaouli (Melaleuca viridiflora Sol. ex Gaertn.) at 2% concentration inhibited the growth of X. perforans in the in vitro assays and consistently reduced the incidence and severity of BLS in planta tests. Negative effects on seed germination and seedling growth were not observed when tomato seeds were treated with the essential oils of eucalyptus and rosemary. Therefore, eucalyptus and rosemary oils can be used for seed treatment to control BLS in tomato. Further investigation is required on the shelf life of these oils, mode of action and their effects on other seedborne pathogens of tomato and in other crop systems in Tanzania.

Eczemas due to plant allergens in manufactured products.

Intolerance to plant allergens in manufactured products is widespread. Results of epidemiological investigations in STRASBOURG are given. The rate of allergy to sesquiterpenic lactones has fallen since 1974, due to the fact that the use of an ointment containing these lactones has decreased. Disguised forms of allergens are reviewed, for instance limonene of Niaouli oil (Biogaze), colophony of "hypoallergenic" tapes or of testing material. Chemical investigations are useful in prevention and in allergological control of medicaments.