Ultrasonic-assisted extraction and UHPLC determination of ascorbic acid, polyphenols, and half-maximum effective concentration in Citrus medica and Ziziphus spina-christi fruits using multivariate experimental design

This study aimed to determine the concentrations of ascorbic acid and polyphenols in fruits and peels of Citrus medica and Ziziphus spina-christi grown in Ethiopia. Conditions of ultrasound-assisted extraction (UAE) and ultra-high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) were optimized, using a multivariate experimental design. The optimum conditions of UAE were 15 min extraction time at 35 ℃, with 75 % aqueous methanol as solvent, and a fruit powder-to-solvent ratio (m/v) of 1:15. Among the different drying conditions investigated, freeze-drying was found to be appropriate for analyzing ascorbic acid, polyphenols, and antioxidant potential. The overall ranges, across the fruits and peels, of ascorbic acid, total polyphenols, and antioxidant potentials (EC50) obtained were 8.7 ± 1.4-91.2 ± 2.6 mg/100 g, 253.0 ± 6.3-764.1 ± 25.8 mg GAE/100 g and 2.4 ± 0.1-26.1 ± 2.9 mg/mL, respectively. This indicates that the fruits and peels of the studied plants are advantageous as sources of ascorbic acid and polyphenols.

In silico Molecular Docking Approach to Identify Potential Antihypertensive Compounds from Ajuga integrifolia Buch.-Ham. Ex D. Don (Armagusa)

Background

Ajuga integrifolia (Armagusa) is used as a decoction to treat high blood pressure and diabetes, widely in Ethiopia. Specific compounds for anti-hypertension activity were not identified so far. This study aims to provide a scientific basis for the therapeutic use of A. integrifolia as an antihypertension agent.

Methods

In silico studies were used to evaluate the antihypertensive components of A. integrifolia. Flavonoids identified using HPLC analysis and iridoid glycosides isolated from A. integrifolia in this study and those isolated from synonyms (A. remota and A. bractosa) were considered in the molecular docking study. Interactions were studied by using Autodock vina (1.2) on PyRx 0.8 and visualizing in 2D and 3D using ligPlot+ and Discovery studio software. Activities like vasoprotection and druglikeness properties were predicted using online servers.

Results

Flavonoids such as quercetin, myricetin, and rutin were identified and quantified by HPLC analysis from different extracts of A. integrifolia. Reptoside and 8-O-acetylharpgide isolated from the aerial part of A. integrifolia. The binding energies of all 17 candidates considered in this study range from -10.2 kcal/mol to -7.5 kcal/mol and are lower than enalapril (reference drug: -5.9 kcal/mol). The binding energies, in most case, constitute hydrogen bonding. Biological activity predicted using PASS test also showed that the flavonoids have more probability of activity than the iridoid glycosides. Druglikeness properties of the candidate molecules showed that most follow the Lipinski rule of five with few violations.

Conclusion

Lower binding energies involving hydrogen bonding and predicted activities concerning hypertension confirm the traditional use of the aerial part of the medicinal plant concerned. Flavonoids: rutin, myricetin, quercetin, and kaempferol take the leading role in the antihypertensive activity of the aerial part of A. integrifolia. The iridoid glycosides studied are almost similar in their effect on their antihypertensive activity and still better than the reference drug.

Method optimization for the determinations of selected phytochemicals and antioxidant activities of wild Ethiopian Syzygium guineense fruit and seed under different drying conditions

This study aimed to optimize the ultrasound-assisted extraction (UAE) parameters using response surface methodology (RSM) for the determination of ascorbic acid (AA), antioxidant activities/the half maximal effective concentration (EC50), total phenolic contents (TPC), and total flavonoid content (TFC) of Ethiopian wild Syzygium guineense fruit and seed processed under different drying conditions. The optimizations of the UAE methods for the determination of AA, antioxidant activities (EC50 values), TPC, and TFC were evaluated using response surface methodology (RSM). The extraction time of 15 min, the temperature of 35 °C, extraction solvent composition (methanol:water) of 75 to 25%, and solid-to-solvent ratios of 1:15 w/v were the optimum independent parameters. The experimental and the predicted data of TPC, EC50, and AA were in good agreement with the overall error below 0.01%. It also indicated a hypothesized distribution of predicted data fitted with experimental data. The average TPC, EC50, and AA content in S. guineense fruits and the seed varied from 581.25 ± 37.13 to 1917.40 ± 26.15 mg GAE/100 g, 4.02 ± 0.42 to 155.73 ± 5.11 mg/100 g, and 1.96 ± 0.02 to 0.94 ± 0.00 mg/mL, respectively. This study indicated that this underutilized wild fruit and its seeds can be an alternative source of AA and antioxidant compounds.

Antioxidant Activity of Flavonoids and Phenolic Acids from Dodonaea angustifolia Flower: HPLC Profile and PASS Prediction

Background. Dodonaea angustifolia is a known medicinal plant across East Arica. The flower of D. angustifolia is not well investigated in terms of phytochemistry and biological activities. This study aims to investigate the presence of flavonoids and phenolic acids in the flower of D. angustifolia and its antioxidant activity. Methods. Preliminary phytochemical screening was carried out using the standard protocols. Antioxidant activity evaluation using DPPH assay and total phenol content (TPC) and total flavonoid content (TFC) determinations in the flower extract were compared with the values of the leaf extract. UHPLC-DAD analysis was managed to develop the profile of the flower extract. Prediction of biological activity spectra for substances (PASS) was done using an online server for antioxidant and related activities. Results. Preliminary phytochemical screening and TPC and TFC values confirmed the presence of flavonoids and phenolic acids. From the HPLC analysis of flavonoids, quercetin, myricetin, rutin, and phenolic acids such as chlorogenic acid, gallic acid, and syringic acid were detected and quantified. The biological activity spectrum was predicted for the detected and quantified polyphenols. Conclusions. D. angustifolia flower is a rich source of flavonoids and phenolic acids, which are extractable and can be checked for further biological activity. It was possible to identify and quantify phenolic compounds through HPLC analysis in the methanol extract of D. angustifolia flower. The PASS biological activity prediction results showed that there were stronger antioxidant activities for the identified flavonoids. Future work will emphasize the isolation and characterization of active principles responsible for bioactivity.

Targeted HPTLC Profile, Quantification of Flavonoids and Phenolic Acids, and Antimicrobial Activity of Dodonaea angustifolia (L.f.) Leaves and Flowers

In East Africa, Dodonaea angustifolia (L.f.) is a well-known medicinal herb. Its leaf is primarily studied in light of its ethnobotanical use. In terms of phytochemistry and biological activity, its flower is not studied. In a prior study, our team looked into phytochemical screening, antioxidant activity, and total phenolic levels. This study aims to compare the profiles and biological activities of the leaf and flower samples of D. angustifolia and to present therapeutic alternatives. The leaf and flower sample powders were extracted with methanol using ultrasound-assisted extraction (UAE). HPTLC profile was obtained using CAMAG-HPTLC equipped with VisionCATS software. Antimicrobial agar well diffusion assay and minimum inhibition concentration (MIC) were determined. The leaf and flower extracts of D. angustifolia showed antibacterial activity with a MIC value of 20 µg/mL against Enterococcus faecalis and Listeria monocytogenes. Similarly, 40 µg/mL was found to be effective against Aspergillus flavus. D. angustifolia flower is a rich source of flavonoids and phenolic acids. Because of its antibacterial properties and profile, which are almost the same, the flower is emerging as a viable option for medicinal alternatives.

Flavonoids and Phenolic Acids from Aerial Part of Ajuga integrifolia (Buch.-Ham. Ex D. Don): Anti-Shigellosis Activity and In Silico Molecular Docking Studies

Shigellosis is one of the major causes of death in children worldwide. Flavonoids and phenolic acids are expected to demonstrate anti-shigellosis activity and anti-diarrheal properties. The aerial part of A. integrifolia is commonly used against diarrhea. This study aimed to identify flavonoids and phenolic acids responsible for this therapeutic purpose. Antioxidant activity, total phenol content, and total flavonoid content were determined. The antibacterial activity of the aerial part against Shigella spp. was also tested using the agar well diffusion method. HPLC analysis was performed using UHPLC-DAD for different extracts of the aerial part. Autodock Vina in the PyRx platform was used to screen responsible components. Ciprofloxacin was used as a reference drug. An enzyme taking part in pyrimidine biosynthesis was used as a target protein. Molecular docking results were visualized using Discovery Studio and LigPlot1.4.5 software. Antioxidant activity, total phenol content, and total flavonoid content are more significant for the aerial part of A. integrifolia. From HPLC analysis, the presence of the flavonoids, quercetin, myricetin, and rutin and the phenolic acids gallic acid, chlorogenic acid, and syringic acid were identified from the aerial part of A. integrifolia. Regarding the antibacterial activity, the aerial part shows considerable activity against Shigella spp. Binding energies, RMSD and Ki values, interaction type, and distance are considered to identify the components most likely responsible for the therapeutic effects and observed activity. Antioxidant activity, total phenol content, and total flavonoid content of the aerial part are in line with anti-shigellosis activity. The top five components that are most likely potentially responsible for therapeutic purposes and anti-shigellosis activity are chlorogenic acid, rutin, dihydroquercetin, dihydromyricetin, and kaempferol.

Heavy metal contents in bovine tissues (kidney, liver and muscle) from Central Gondar Zone, Ethiopia

Environments prone to naturally non-biodegradable metal pollution have remained hot areas of research. Here, concentrations of Cu, Cr, Cd and Pb in 90 bovine tissue (kidney, liver and muscle) samples collected from Gondar City abattoir and Nara-Awudarda in Central Gondar Zone, Ethiopia, were investigated. The samples were dry-ashed at 550 °C for 3.45 h, mineralized with 2 mL conc. HNO₃, and analysed using flame atomic absorption spectrometer. Pattern recognition methods, viz. principal component analysis (PCA) and partial least squares - discriminant analysis (PLS-DA), were employed to investigate heavy metal profiles in bovine tissues and classify them based on their geographic source. Results showed that the mean concentrations of the metals (mg/kg) extended in the range: 1.5-11.5 (Cu), 0.42-1.5 (Pb), BDL-1.05 (Cr) and BDL-0.41 (Cd). The concentrations of Cu and Cd, except Cd in muscle samples from Gondar City abattoir, were below the permissible limits while Pb and Cr, except for Pb in kidney and Cr in all samples at Gondar City abattoir, were above the permissible limits. Hence, it calls for enforceable food safety monitoring practices. PCA visualizes grouping of the studied bovine tissues based on the contents of analyzed metals where liver contained highest concentrations of the studied metals, except for Cd, which was highest in kidney. PLS-DA model clearly classified the tissue samples into two clusters depending on their geographic source. In general, the accumulation burden of heavy metals exhibited tissue-specific and sample source differences, probably due to varied organ functions and environmental conditions.