María Belén Agüero

Essential Oils of Medicinal Plants from the Central Andes of Argentina: Chemical Composition, and Antifungal, Antibacterial, and Insect-Repellent Activities

The antifungal, antibacterial, and insect‐repellent activities of the essential oils (EOs) of Acantholippia seriphioides, Artemisia mendozana, Gymnophyton polycephalum, Satureja parvifolia, Tagetes mendocina, and Lippia integrifolia, collected in the Central Andes area, province of San Juan, Argentina, were investigated. The dermatophytes Microsporum gypseum, Trichophyton mentagrophytes, and T. rubrum were inhibited by the EOs of G. polycephalum, L. integrifolia, and S. parvifolia, with minimum inhibitory concentrations (MICs) between 31.2 and 1000 μg/ml. Moreover, all EOs presented moderate activity against the bacteria tested, and the L. integrifolia and G. polycephalum EOs showed excellent repellent properties against Triatoma infestans, the Chagas disease vector, with repellency values between 60 and 100%. The A. seriphioides, G. polycephalum, and L. integrifolia EOs, obtained by hydrodistillation, were characterized by GC‐FID and GC/MS analyses. The highest number of components (40) was identified in L. integrifolia EO, which, along with that of A. seriphioides, contained important amounts of oxygenated monoterpenes (44.35 and 29.72%, resp.). Thymol (27.61%) and carvacrol (13.24%) were the main components of A. seriphioides EO, and borneol, lippifoli‐1(6)‐en‐5‐one, and terpinen‐4‐ol (>8.5%) were the principal compounds of L. integrifolia EO. These results support the idea that oxygenated monoterpenes are the bioactive fractions of the EOs. Finally, the study shows that these Andean species might be used to treat superficial fungal infections and to improve the local Chagas disease situation by vector‐control.

ANTIMICROBIAL ACTIVITY OF EXTRACTS, ESSENTIAL OIL AND METABOLITES OBTAINED FROM TAGETES MENDOCINA

Extracts from the Argentinean herb Tagetes mendocina Phil. (Asteraceae) were tested for antimicrobial activity against fungi, bacteria and protozoa. The different extracts (PE, DCM, MeOH and EtOAc) and the essential oil displayed activity mainly against dermatophytes, a group of fungi that produces skin infections. The bioassay-guided fractionation of PE, DCM and EtOAc extracts led to the isolation of eight compounds including two thiophenes, two acetophenone derivatives, dihydrorosefuran and three flavonoids. The thiophenes 5-(4-hydroxy-1-butynyl)-2,2 ’ -bithienyl (BBTOH) (1) and its acetate (BBTOAc) (2) proved to be highly active against the dermatophytes Microsporum gypseum, Trichophyton rubrum and T. mentagrophytes with MIC values of 3.12, 3.12 and 6.25 µg/mL for compound 1 and 25, 3.12 and 6.25 µg/mL for compound 2, respectively. In turn, the essential oil displayed a weak to moderate antifungal effect against M. gypseum with MIC = 250 µg/mL. The essential oil was examined by GC and GC-MS and 21 constituents (97.3%) were identified. ( E) β-ocimene, (Z)-tagetone, (E)-tagetone, (Z)-ocimenone, α-pinene and (E)-ocimenone were the major components. In addition, thiophenes 1 and 2 and 2-hydroxyacetophenone 3 showed antiprotozoal activity against Leishmania amazonensis, L. brasiliensis and L. infantum promastigotes with 100% lysis at 100 µg/mL.

Cholinesterase-inhibitory effect and in silico analysis of alkaloids from bulbs of Hieronymiella species

BACKGROUND In Argentina, the Amaryllidaceae family (59 species) comprises a wide variety of genera, only a few species have been investigated as a potential source of cholinesterases inhibitors to treat Alzheimer disease (AD). PURPOSE To study the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of the basic dichloromethane extracts (E) from Hieronymiella aurea, H. caletensis, H. clidanthoides, H. marginata, and H. speciosa species, as well as the isolated compounds from these plant extracts. STUDY DESIGN AND METHODS AChE and BChE inhibitory activities were evaluated with the Ellmans spectrophotometric method. The alkaloids composition from the E was obtained by gas chromatography-mass spectrometry (GC-MS). The E were successively chromatographed on a silica gel column and permeated on Sephadex LH-20 column to afford the main alkaloids identified by means of spectroscopic data. Additionally, an in silico study was carried out. RESULTS Nine known alkaloids were isolated from the E of five Hieronymiella species. Galanthamine was identified in all the species by GC-MS standing out H. caletensis with a relative abundance of 9.79% of the total ion current. Strong AChE (IC50 = 1.84 - 15.40 µg/ml) and moderate BChE (IC50 = 23.74 - 136.40 µg/ml) inhibitory activities were displayed by the extracts. Among the isolated alkaloids, only sanguinine and chlidanthine (galanthamine-type alkaloids) demonstrated inhibitory activity toward both enzymes. The QTAIM study suggests that sanguinine has the strongest affinity towards AChE, attributed to an additional interaction with Ser200 as well as stronger molecular interactions Glu199 and His440.These results allowed us to differentiate the molecular behavior in the active site among alkaloids possessing different in vitro inhibitory activities. CONCLUSION Hieronymiella species growing in Argentina represent a rich and widespread source of galanthamine and others AChE and BChE inhibitors alkaloids. Additionally, the new trend towards the use of natural extracts as pharmaceuticals rather than pure drugs opens a pathway for the development of a phytomedicine derived from extracts of Hieronymiella spp.

The activity of propolis in the scavenging of vitamin B2-photogenerated ROS

Objectives: The study was focused on the activity of propolis from Amaicha del Valle, Argentina (ProAV) as a promoter and scavenger of Riboflavin (Rf) – photogenerated reactive oxygen species (ROS). Methods: Through a kinetic and mechanistic study, employing stationary and time-resolved photochemical and electrochemical techniques, the protecting activity of ProAV was investigated. Results: In the absence of light and Rf, ProAV exerted a relatively efficient inhibitory effect on 1,1-diphenyl-2-picrylhydrazyl radicals and acts as a protector of artificially promoted linoleic acid oxidation. Under aerobic visible-light-irradiation conditions, in the presence of Rf as the only light-absorber species, a complex picture of competitive processes takes place, starting with the quenching of singlet and triplet electronically excited states of Rf by ProAV. The species O2(1 g), O2•−, H2O2, and OH• are generated and interact with ProAV. Discussion: ProAV behaves as an efficient ROS scavenger. It is scarcely photo-oxidized by interaction with the mentioned ROS. Quantitative results indicate that ProAV is even more resistant to photo-oxidation than the recognized antioxidant trolox. Two dihydroxychalcones, mostly present in the ProAV composition, are responsible for the protecting activity of the propolis.

Antimicrobial and antioxidant activities of Gentianella multicaulis collected on the Andean Slopes of San Juan Province, Argentina.

The infusion of the aerial parts of Gentianella multicaulis (Gillies ex Griseb.) Fabris (Gentianaceae), locally known as ‘nencia’, is used in San Juan Province, Argentina, as stomachic and as a bitter tonic against digestive and liver problems. The bioassay-guided isolation of G. multicaulis extracts and structural elucidation of the main compounds responsible for the antifungal and free radical scavenging activities were performed. The extracts had strong free radical scavenging effects in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay (45 - 93% at 10 μg/mL) and ferric-reducing antioxidant power (FRAP) assay at 200 μg/mL. Demethylbellidifolin (4) had high antioxidant activity in the DPPH and FRAP assay. The dermatophytes Microsporum gypseum, Trichophyton mentagrophytes, and T. rubrum were moderately inhibited by the different extracts (MIC values of 125 - 250 μg/mL). Demethylbellidifolin (4), bellidifolin (5), and isobellidifolin (6) showed an antifungal effect (MIC values of 50 μg/mL), while swerchirin (3) was less active with a MIC value of 100 μg/mL. In addition, oleanolic acid (1) and ursolic acid (2) were also isolated. These fi ndings demonstrate that Gentianella multicaulis collected in the mountains of the Province of San Juan, Argentina, is an important source of compounds with antifungal and antioxidant activities.