Abstract
The essential oil (EO) composition of
The yield of EO obtained from the samples by distillation was 0.9% ± 0.2% v/w (average of 2 extractions on dry weight basis). Comparable results were previously reported for the EO extraction in
Chemical Composition of
Results are expressed as relative percentage in the mixture.
aCompounds identified by comparison of their RI (retention indices) and mass spectra with literature data, the MS library (NBS 75K, NIST98), and a spectra library built up from pure substances and components of known oils.
bExperimental RI on HP5 MS capillary column in reference to C7-C24 n-alkanes.
dCompounds listed in order of elution, tR (min).
ePercentage peak area of EO components as means of 2 determinations ± standard deviation.
ftr: traces (<0.1%).
The high-performance liquid chromatography diode array detector (HPLC-DAD) analysis of extracts of rica-rica allowed the determination of 21 phenolic compounds. The identified compounds comprise 6 phenolic acids and derivatives (
Phenolic Compounds in
HE, hydroethanolic extract; WE, decoction extract.
aComposition of extracts as mean ± standard deviation of three assays (mg/kg or µg/g).
bRelative percentage of compounds in brackets.
The antibacterial activity of EO and polar extracts was investigated herein; minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) values were determined against 6 pathogenic bacteria (Table 3). Gram-positive strains were more sensitive to rica-rica extracts than Gram-negative ones, mainly with HE; similar results were previously reported in other studies.
3,4,15,19
EO and extracts of rica-rica evidenced higher activity against
Antibacterial Activity (MIC and MLC) of Acantholippia salsoloides Extracts (mg/mL) and Essential Oil (mL/mL).
a
aMIC, minimum inhibitory concentration; MLC, minimum lethal concentration. Results are from 3 independent experiments performed in duplicate. Strong activity is for MIC = 0.05-0.5 mg/mL, moderate activity for MIC = 0.6-1.5 mg/mL, and weak activity above 1.5 mg/mL. 15
Regarding polar extracts, the antifungal potential of HEs of
The antimicrobial activity depends not only on the amount of specific compounds in EO and extracts, but also on the type of compounds in the phytocomplex.
12
The antibacterial properties of
The antioxidant activity of HE and WE was tested against DPPH·, superoxide (O2
·
−), and nitric oxide (NO·) radicals.
IC50 (mg/mL) Values Found in the Antioxidant Activity and α-Glucosidase Assays for HE and WE.
BHT, butylated hydroxytoluene; IC50, half-maximal inhibitory concentration; HE, hydroethanolic extract; WE, decoction extract.
a, b, cDifferences between extracts were tested for significance using the one-way analysis of variance with post hoc Tukey’s test. Differences were considered significant for
The main phenolic compounds present in rica-rica extracts (cynaroside and isoferulic acid) are found in several medicinal plants and food matrices. These phytochemicals have demonstrated to have several beneficial effects on human health. Cynaroside among other apigenin and luteolin derivatives was previously isolated from
The potential of
In relation to the volatile fraction, a
Experimental
Plant Samples
Aerial parts of 12 specimens (100-200 g each one) were collected during the flowering period, April of 2013, in Chucalezna (23° 21′ 39.3″ S, 65° 19′ 20.9″ O, 2702 masl), Jujuy Province (Argentina). The plant material was identified by Professor Osvaldo Ahumada (National University of Jujuy, Argentina) and Professor Gustavo Giberti (National University of Buenos Aires, Argentina); a voucher specimen (HN1308) was deposited in the Herbarium of PRONOA (National University of Jujuy, Argentina). The plant material (leaves and flowers) was dried at room temperature for 7 days, ground to powder in a blender (mean particle size <2 mm) and stored at −20°C until required.
Preparation of Extracts
EO was obtained from 500 g dry material by steam distillation for 2.5 hours using a Clevenger-type apparatus. 15 The collected oil was dried and stored at 4°C until analysis. The EO content was determined volumetrically on dried weight basis. WE was prepared boiling 5 g of dried material in 100 mL of H2O for 10 minutes. 15 The resulting extracts were filtered through a Büchner funnel, frozen, and lyophilized. HE was prepared with 5 g of dried samples, and sonicated at 40°C with 100 mL of ethanol:water (70:30 v:v) for 20 minutes. 15 The obtained extract was evaporated under reduced pressure and kept at −20°C for further analysis. Extractions were carried out in triplicate.
Analysis of the Essential Oil
EO composition was analyzed by gas chromatography mass spectrometry and gas chromatography flame ionization detector using a previously described procedure. 15 The quantification of each compound was performed on the basis of their GC/FID peak areas without the use of response factor corrections. 16 –18
Analysis of Phenolic Compounds
WE and HE were redissolved in methanol and filtered through a 0.45 µm polytetrafluoroethylene membrane. The phenolic compounds were analyzed in an HPLC/DAD (Gilson) using the previously described procedure.
15
Thirty microliters of each polar extract were analyzed with an analytical HPLC unit (Gilson), using a Spherisorb ODS2 (25.0 × 0.46 cm; 5 µm, particle size; Waters, Milford, MA) column. The chromatograms were recorded at 280 (tannins), 320 (phenolic acids), and 350 nm (flavonoids). The data were processed in Unipoint System software (Gilson Medical Electronics, Villiers-le-Bel, France). The compounds in each sample were identified by comparing their retention times and UV spectra with the library of spectra. The quantification was achieved by measuring the absorbance recorded in the chromatograms relative to external standards. This procedure was performed in triplicate. Phenolic acid derivatives were quantified as 5-
Antibacterial Activity
The study included 6 bacterial strains:
Antioxidant Activity
The scavenging activity against DPPH·, O2 · −, and ·NO radicals was evaluated for WE and HE according to Celaya et al 15 Three independent assays were performed for each radical in triplicate. IC50 values represent the concentrations that caused 50% activity loss. Statistical analysis was carried out using Graph pad Prism 5 Software (San Diego, CA, USA). For the DPPH· scavenging activity, the antioxidant BHT was used as reference compound.
α-Glucosidase Inhibitory Activity
The effect on α-glucosidase was assessed using a previously reported procedure. 15
Footnotes
Acknowledgments
The authors thank Cristina E. Mayol and Carlos D. Galli for their critical English revision and thank Ana C. Molina for her support and collaboration.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Project SeCTER-UNJu, Aromatic and Medicinal Plants of NWA, SPU UNJu-1711, Project UNaM 16/Q1119-PI, FEDER funds POCI - COMPETE 2020- Operational Program Competitiveness and Internationalization in Axis I – Strengthening research, technological development and innovation (Project POCI-01–0145-FEDER-007491), Operational Program of the Center (Project CENTRO-01–0247-FEDER-017547), and National Funds by “Fundação para a Ciência e Tecnologia” - FCT (Project UID/Multi/00709/2013).
