The use of plants as sources for novel antimicrobial as well as antioxidant agents offers advantages. Plants are readily accessible and inexpensive, extracts or compounds from plant sources often demonstrate high level of biological activities. Previous studies have reported antibacterial and antifungal activities within the Fabaceae family that included Acacia species. This study aims to determine presence of antibacterial activity, antioxidant activity, and the secondary metabolites of sequential solvent extracts (acetone, methanol, and acetic acid) of Acacia berlandieri and Acacia rigidula leaves. The antibacterial activity was investigated using a disc diffusion assay. The ferric thiocyanate method was used to assess the ability of all extracts to prevent oxidation. Qualitative phytochemical tests, NMR, IR, and UV–Vis spectroscopy were done to identify potential secondary metabolites. P. alcalifaciens (p < 0.001), E. faecalis (p < 0.01), S. aureus (p < 0.001), and Y. enterocolitica (p < 0.001) were significantly inhibited by A. rigidula extracts when compared to A. berlandieri extracts. A. rigidula’s acetone extract exhibited the significantly (p < 0.001) highest inhibition of peroxidation, 42%. Qualitative phytochemical tests showed positive results for presence of phenols, flavonoids, saponins, terpenes and tannins. NMR, IR, and UV–Vis spectroscopy revealed chemical structures found in flavonoids, saponins, terpenes and tannins, supporting the results of qualitative phytochemical tests. A. berlandieri and A. rigidula leaf extracts have revealed presence of medicinally valued bioactive components. The results of this study provide a basis for further investigations of the A. rigidula leaf extracts. A. rigidula leaf extracts have the potential to serve as a source of novel antimicrobial and antioxidant agents.
Graphic abstract
Two new water-soluble ruthenium hydrides Cp′Ru(PTA) 2 H, Cp′ = C 9 H 7 − (Ind, 1) or C 8 H 9 − (Dp, 2), along with IndRu(PTA) 2 Cl (3) have been synthesized. DpRu(PTA) 2 H was synthesized by refluxing DpRu(PTA) 2 Cl with NaCO 2 H in methanol. IndRu(PTA) 2 H was unable to be generated in a similar manner due to complications in the synthesis of IndRu(PTA) 2 Cl. IndRu(PTA) 2 H was synthesized by conversion of the mixed-phosphine ruthenium complex IndRu(PTA)(PPh 3 )Cl into IndRu(PTA)(PPh 3 )H followed by ligand substitution of PPh 3 with 1,3,5-triaza-7-phosphaadamantane (PTA). Complexes 1 and 2 are stable and moderately soluble in water (S 25°C = 16 mg/mL for 1 and ∼20 mg/mL for 2). The Ru hydrides react with chlorinated solvents, in the case of 1 yielding the challenging synthesize IndRu(PTA) 2 Cl (3) (S 25°C = 17 mg/mL). The synthesis, isolation, and reactivity of 1−3 are described including crystal structures of 1, 2, 3, and [IndRu(PTA) 3 ](Cl). H/D exchange reactions of 1 with D 2 O were monitored by 31 P NMR spectroscopy as a function of temperature: ΔH ‡ = 92 ± 3 kJ/mol, ΔS ‡ =−22 ± 2 J/mol• K. In addition, H/D exchange reactions of the 1,2-dihydropentalenyl (η 5 -C 8 H 9 − , Dp) analogue, 2, with D 2 O are also described along with the effects of pH on the 31 P NMR spectra.
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