Helichrysum genus was used in folk South African medicine to treat various human disorders. As a part of our on-going research addressing the exploitation of South African plants belonging to this genus, five species were investigated for their volatile and antimicrobial activities. The volatile organic compounds (VOCs) and the essential oils (EOs) were analysed by gas chromatography mass spectrometry (GC-MS). Microdilution was the method used for assessing both antimycotic and antibacterial activities, which was also tested by Kirby-Bauer agar disc diffusion. Total monoterpenes (TMs) dominated the VOCs of four species (H. trilineatum (70.6%), H. edwardsii (79.3%), H. cooperi (84.5%), and H. pandurifolium (57.0%)). H. cooperi and H. edwardsii EOs showed the predominance of TMs (68.2% and 84.5%, respectively), while H. pandurifolium and H. trilineatum EOs were characterized by the prevalence of TSs (86.5% and 43.6%, respectively). H. odoratissimum EO evidenced a similar amount of both TMs (49.5%) and TSs (46.4%). Microsporum canis was more sensitive to these EOs. The lowest minimum inhibitory concentration (MIC) was observed with H. pandurifolium and H. edwardsii EOs (0.25%). H. pandurifolium and H. trilineatum had a good effect on Staphylococcus aureus (MIC 5%). These findings open new perspectives for the exploitation of these natural compounds for application in cosmetics and pharmaceutics.

Spontaneous emissions of S. dentata Aiton and S. scabra Thunb., as well as the essential oil (EO) composition of the cited species, together with S. aurea L., were investigated. The chemical profile of the first two species is reported here for the first time. Moreover, in vitro tests were performed to evaluate the antifungal activity of these EOs on Trichophyton mentagrophytes, Microsporum canis, Aspergillus flavus, Aspergillus niger, and Fusarium solani. Secondly, the EO antibacterial activity against Escherichia coli, Staphylococcus aureus, and Staphylococcus pseudointermedius was examined, and their antiviral efficacy against the H1N1 influenza virus was assessed. Leaf volatile organic compounds (VOCs), as well as the EOs obtained from the arial part of Salvia scabra, were characterized by a high percentage of sesquiterpene hydrocarbons (97.8% and 76.6%, respectively), mostly represented by an equal amount of germacrene D (32.8% and 32.7%, respectively). Both leaf and flower spontaneous emissions of S. dentata, as well as the EO composition, showed a prevalence of monoterpenes divided into a more or less equal amount of hydrocarbon and oxygenated compounds. Interestingly, its EO had a non-negligible percentage of oxygenated sesquiterpenes (29.5%). S. aurea EO, on the contrary, was rich in sesquiterpenes, both hydrocarbons and oxygenated compounds (41.5% and 33.5%, respectively). S. dentata EO showed good efficacy (Minimal Inhibitory Concentration (MIC): 0.5%) against M. canis. The tested EOs were not active against E. coli and S. aureus, whereas a low inhibition of S. dentata EO was observed on S. pseudointermedius (MIC = 10%). Once again, S. dentata EO showed a very good H1N1 inhibition; contrariwise, S. aurea EO was completely inactive against this virus. The low quantity of S. scabra EO made it impossible to test its biological activity. S. dentata EO exhibited interesting new perspectives for medicinal and industrial uses.

AbstractIn the present work the composition of biogenic volatile organic compounds (BVOCs) and the essential oil (EO) of Helichrysum araxinum Takht. ex Kirp. aerial parts, together with the antimicrobial activity, were investigated. The results showed the prevalence of sesquiterpene hydrocarbons in both spontaneous emissions as well as in the EO. The main compounds of BVOCs were γ-curcumene (10.7%), γ-muurolene (9.2%), and β-selinene (8.5%). This latter constituent also showed a similar amount in the EO and represented the most abundant compounds together with α-selinene (8.0%). It is Interesting to note the same percentage of monoterpene hydrocarbons (MHs) in both the aroma profile and the EO (18.0%) with the same most abundant compounds: β-pinene (6.3% in BVOCs vs. 5.1% in EO, respectively) and limonene (4.5% in VOCs vs. 4.9% in EO, respectively). With regard to the antimycotic activity, the EO showed to be inactive against the tested strains, while a moderate antibacterial activity was shown against Staphylococcus isolates.

The volatiloma of four Helichrysum species (H. anomalum, H reflexum, H. retortum and H. rugulosum) was analysed here for the first time by GC-MS for a chemotaxonomic contribution to this genus. Sesquiterpene hydrocarbons (SHs) prevailed in the aroma profile (VOCs) of H. reflexum, H. rugulosum and H. anomalum (74.7%, 93.6% and 41.6%, respectively), even though the main compounds were different (β-caryophyllene, α-humulene and α-copaene, respectively).The VOCs of H. retortum showed a high percentage of aliphatic hydrocarbons (NTs, 77.7%) mainly represented by octyl ether. The essential oil composition of each of H. rugulosum and H. retortum followed the same trend as VOCs related to the main class (SHs and NTs, respectively). In H. reflexum EO, the SHs were replaced by oxygenated sesquiterpenes (OS, 49.0%) with caryophyllene oxide as the main compound, while in H. anomalum the SHs were swapped in NTs (37.3%).

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