Phytochemical and antioxidant-related investigations on bark of Abies spectabilis (D. Don) Spach. from Nepal

The Bark of Picea abies L., a Waste from Sawmill, as a Source of Valuable Compounds: Phytochemical Investigations and Isolation of a Novel Pimarane and a Stilbene Derivative

In this work, the sawmill waste from Picea abies debarking was considered as source of valuable phytoconstituents. The extraction was performed using different ethanol/water mixtures, and characterization was obtained by LC-MSⁿ. This latter revealed flavonoid glycosides, lignans, and procyanidins. Extraction with organic solvents (dichloromethane and methanol) and chromatographic separations of the obtained extracts by silica column followed by semi-preparative HPLC led to the isolation of polyphenols and terpenoids such as 21α-metoxy-serrat-14-en-3-one, 21α-hydroxy-serrat-14-en-3-one, pinoresinol, dehydroabietic acid, 15-hydroxy-dehydroabietic acid, 7-oxo-dehydroabietic acid, pimaric acid, 9β-pimara-7,15-dien-19-ol, 13-epi-manoyl oxide, taxifolin-3'-O-glucopyranoside, trans-astringin, and piceasides. Piceaside V and 9β-pimara-7-keto-19β-olide, two novel compounds identified for the first time in P. abies bark, were isolated, and their structures were elucidated using 1D and 2D NMR and MS techniques. The polyphenolic composition of the methanolic portion was also investigated using LC-MSⁿ, and the piceaside content was estimated. To assess the antioxidant activity of main constituents, semi-preparative HPLC was performed on the methanolic extract, and the obtained fractions were assayed by using the DPPH test. Overall, this work shows the potential usefulness of P. abies bark as a source of valuable phytochemicals.

Antifungal and Antibacterial Activities of Wood Treated with Musa paradisiaca L. Peel Extract: HPLC Analysis of Phenolic and Flavonoid Contents

In the present study, Melia azedarach wood samples that were treated with the methanolic extract of Musa paradisiaca L. peels were evaluated for their antibacterial and antifungal activities against Agrobacterium tumefaciens, Dickeya solani, Erwinia amylovora, Pseudomonas cichorii, Serratia pylmuthica, Fusarium culmorum, and Rhizoctonia solani. The strongest antibacterial activity was only found against A. tumefaciens (inhibition zone 90 mm), while the other bacterial strains showed resistance to wood that was treated with the extract. Potential antifungal activity against F. culmorum and R. solani was observed; the mycelial growth inhibition percentages reached 68.88% and 94.07%, respectively, in wood samples that were treated with the 3% methanolic extract of M. paradisiaca peel. HPLC analysis demonstrated the presence of seven phenolic compounds and three flavonoid compounds, as their peaks were matched with the standard compounds in a HPLC analysis. The major constituents of phenolic and flavonoid compounds in mg/100 g dry extract (DE) were ellagic acid (16.19), gallic acid (7.73), rutin (973.08), myricetin (11.52), and naringenin (8.47). The results demonstrated the potential effects of banana peel extract as a natural compound that can protect wood from molds while in use.

Antifungal, Antibacterial, and Antioxidant Activities of Acacia Saligna (Labill.) H. L. Wendl. Flower Extract: HPLC Analysis of Phenolic and Flavonoid Compounds

In this study, for the environmental development, the antifungal, antibacterial, and antioxidant activities of a water extract of flowers from Acacia saligna (Labill.) H. L. Wendl. were evaluated. The extract concentrations were prepared by dissolving them in 10% DMSO. Wood samples of Melia azedarach were treated with water extract, and the antifungal activity was examined at concentrations of 0%, 1%, 2%, and 3% against three mold fungi; Fusarium culmorum MH352452, Rhizoctonia solani MH352450, and Penicillium chrysogenum MH352451 that cause root rot, cankers, and green fruit rot, respectively, isolated from infected Citrus sinensis L. Antibacterial evaluation of the extract was assayed against four phytopathogenic bacteria, including Agrobacterium tumefaciens, Enterobacter cloacae, Erwinia amylovora, and Pectobacterium carotovorum subsp. carotovorum, using the micro-dilution method to determine the minimum inhibitory concentrations (MICs). Further, the antioxidant capacity of the water extract was measured via 2,2'-diphenylpicrylhydrazyl (DPPH). Phenolic and flavonoid compounds in the water extract were analyzed using HPLC: benzoic acid, caffeine, and o-coumaric acid were the most abundant phenolic compounds; while the flavonoid compounds naringenin, quercetin, and kaempferol were identified compared with the standard flavonoid compounds. The antioxidant activity of the water extract in terms of IC₅₀ was considered weak (463.71 μg/mL) compared to the standard used, butylated hydroxytoluene (BHT) (6.26 μg/mL). The MIC values were 200, 300, 300, and 100 µg/mL against the growth of A. tumefaciens, E. cloacae, E. amylovora, and P. carotovorum subsp. carotovorum, respectively, which were lower than the positive control used (Tobramycin 10 μg/disc). By increasing the extract concentration, the percentage inhibition of fungal mycelial was significantly increased compared to the control treatment, especially against P. chrysogenum, suggesting that the use of A. saligna flower extract as an environmentally friendly wood bio-preservative inhibited the growth of molds that cause discoloration of wood and wood products.

Preliminary evaluation of quince (Cydonia oblonga Mill.) fruit as extraction source of antioxidant phytoconstituents for nutraceutical and functional food applications

BACKGROUND

Quince (Cydonia oblonga) fruits can be considered as starting material for the extraction of health-promoting phytochemicals, to be exploited in food and nutraceuticals. In the present work, liquid chromatography coupled with diode array detection and tandem mass spectrometry analysis allowed the study of the phytochemical composition of quince fruits and to compare it with those of six commercial apple varieties.

RESULTS

The distribution and quantification of secondary metabolites in peel and pulp were studied and compared with six commercial apple varieties. Furthermore the in vitro antioxidant activity was determined by 2,2-diphenyl-2-picrylhydrazyl (DPPH) assay. Quince fruit presented significant amounts of shikimic and quinic acid derivatives, as well as flavonoids and procyanidins. Compared with apple, quince fruit composition was characterized by the presence of 4-caffeoylshikimic acid, 4-caffeoyl quinic acid, quercetin-3,7-diglucoside, kaempferol-3-O-rhamnoside and kaempferol-7-O-glucoside, and the dihydrochalcones were not detectable. The peel showed the highest contents of phenolics, whereas 3-O-caffeoylquinic acid was the most abundant compound in the quince pulp. The Pearson correlation index was calculated considering the quantitative amount of the phenolic constituents and the radical scavenging activity toward DPPH^· both for peel and pulp extracts.

CONCLUSIONS

This study highlighted the presence of significant amounts of valuable secondary metabolites in quince fruit, in particular the procyanidins and caffeoyl esters with shikimic and quinic acid. Notably, owing to the higher content in phenolic compounds and the stronger antioxidant capacity compared with the other fruits considered, the use of C. oblonga as a source of antioxidant can be valuable in nutraceuticals, revealing new possible applications of quince fruit. © 2018 Society of Chemical Industry.

Larix decidua Bark as a Source of Phytoconstituents: An LC-MS Study

Larix decidua bark is a waste of the timber industry and is widely diffused in Northern Italy. This material can be considered a good source of antioxidants and phytoconstituents with possible use in cosmetic or nutraceutical products. In this study, simple extraction of larch bark was performed using mixtures of ethanol/water. Furthermore, the phytochemical composition of larch bark extract was studied using LC-MSⁿ methods and the main constituents were identified as flavonoids, spiro-polyphenols, and procyanidins. To confirm the identification by LC-MS semi-preparative HPLC was performed in order to isolate the main constituents and verify the structures by ¹H-NMR. Antioxidant properties were studied using an in vitro approach combining DPPH assay and LC-MS in order to establish different roles of the various classes of phytochemicasl of the extract. DPPH activity of some of the isolated compounds was also assessed. The overall results indicate this waste material as a good source of antioxidant compounds, mainly procyanidins, whichresulted the most active constituents in the DPPH assay.

Unveiling the chemistry behind the green synthesis of metal nanoparticles

Nanobiotechnology has emerged as a fundamental domain in modern science, and metallic nanoparticles (NPs) are one of the largest classes of NPs studied because of their wide spectrum of possible applications in several fields. The use of plant extracts as reducing and stabilizing agents in their synthesis is an interesting and reliable alternative to conventional methodologies. However, the role of the different components of such extracts in the reduction/stabilization of metal ions has not yet been understood clearly. Here we studied the behavior of the main components of a Eucalyptus globulus Labill. bark aqueous extract during metal-ion reduction followed by advanced chromatographic techniques, which allowed us to establish their specific role in the process. The obtained results showed that phenolic compounds, particularly galloyl derivatives, are mainly responsible for the metal-ion reduction, whereas sugars are essentially involved in the stabilization of the NPs.