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A concise synthesis of (−)-steviamine is reported along with the synthesis of its analogues 10-nor-steviamine, 10-nor-ent-steviamine and 5-epi-ent-steviamine. These compounds were tested against twelve glycosidases (at 143 μg mL−1 concentrations) and were found to have in general poor inhibitory activity against most enzymes. The 10-nor analogues however, showed 50-54% inhibition of α-L-rhamnosidase from Penicillium decumbens while one of these, 10-nor-steviamine, showed 51% inhibition of N-acetyl-β-D-glucosaminidase (from Jack bean) at the same concentration (760 μM). A concise synthesis of steviamine is reported along with the synthesis of its analogues 10-nor-steviamine, 10-nor-ent-steviamine and 5-epi-ent-steviamine. These compounds were tested against twelve glycosidases (at 143 g/mL concentrations) and were found to have in general poor inhibitory activity against most enzymes. The 10-nor analogues however, showed 50-54% inhibition of -L-rhamnosidase from Penicillium decumbens while one of these, 10-nor-steviamine, showed 51% inhibition of N-acetyl--D-glucosaminidase (from Jack bean) at the same concentration (760 M).

The chemical constituents of the essential oil from the leaves of Gynura divaricata (L.) DC.were investigated by GC-FID and GC-MS. Seventeen compounds, representing 97.1 % of the chromatographical fraction of the oil, were detected. The major constituents, cubenol (65.7 %) and spathulenol (6.4 %), were isolated using column chromatography and identified by NMR and MS analysis. The antioxidant, cytotoxicity and antimicrobial activities of the essential oil, the hexane, dichloromethane and methanol extracts of G. divaricata leaves were investigated. The essential oil and the crude extracts showed antioxidant activity using the ABTS and DPPH methods, respectively. The essential oil exhibited significant cytotoxicity against KB, MCF-7 and NCI-H187 cancer cell lines with the IC 50 values of 5.79, 47.44 and 17.65 μg/mL, respectively and had a MIC of 50 μg/mL against Mycobacterium tuberculosis H 37 Ra. Cubenol had an IC 50 value of 45.37 μg/mL against the NCI-H187 cancer cell line. All extracts were non-cytotoxic against Vero cells. The essential oil and the extracts showed antimicrobial activity using the disc diffusion assay. The methanol extract was the most potent of the three extracts.

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The objective of this study was to evaluate the potential use of the Thai black glutinous rice grain (RG) and black glutinous rice bran (RB) extract in cosmeceutical products. The ethanolic extracts were prepared. Anthocyanin, phenolic, and flavonoid contents in the extracts were determined, and antioxidant activities were evaluated using 2,2-Di(4-tert-octylphenyl)-1-picrylhydrazyl, 2,2ʹ-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and ferric reducing antioxidant power assays. The RB extract exhibited higher total phenolic (129.03 ± 2.44 μg of gallic acid equivalent/mg extract) and flavonoid (7.56 ± 0.40 μg of quercetin equivalent/mg extract) contents than the RG extract. In addition, the antioxidant activities of the RB extract were superior to the activities of the RG extract. Therefore, the RB extract was selected for loading into the water-and oil-based formulations. The stability testing consisted of centrifugation and six heating-cooling cycles. All formulations were stable without noticeable phase separation or aggregation after the stability testing. In addition, the pH values ranged between 5 and 5.5, which was proper for skin application. Our findings indicate that the RB extract is a source of phenolic compounds with antioxidants and suggest that this extract might be a promising active component in skincare products.

Lactuca sativa L. is an economically important vegetable that contains numerous phytochemicals. This study aimed to determine the phytochemicals in three lettuce cultivars (red oak, red coral, and butterhead) and assess their total phenolics, total flavonoids, and antioxidant activities. The dried leaves of each lettuce cultivar were macerated with hexane, ethyl acetate (EtOAc), and 95% ethanol (EtOH). Total phenolics, total flavonoids and antioxidant activities from the three solvent extracts were measured. The phytochemical screening showed that the leaves from the three lettuce cultivars contained flavonoids, hydrolyzable tannins, coumarins, steroids, and phenolic compounds. While the EtOAc fraction of the red coral lettuce showed the highest total phenolic content (9.747 ± 0.021 mg gallic acid equivalent/g) and the hexane fraction of the butterhead lettuce contained the highest flavonoids (7.065 ± 0.005 mg quercetin equivalent/g). In the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay, the EtOAc fraction of the red coral lettuce had the highest antioxidant capacity with an IC50 of 0.277 ± 0.006 mg/mL, whereas, in the ABTS (2,2’-azino-bis(3- ethylbenzothiazoline-6-sulfonic acid)) assay, the 95% EtOH of the red coral lettuce had the highest antioxidant capacity with an IC50 of 0.300 ± 0.002 mg/mL. All three lettuce cultivars contained high levels of phenolic content and flavonoids, which are the source of antioxidant activities. These lettuce cultivars, especially the red coral lettuce, are a potential source of natural antioxidants. Further research on the application of natural antioxidants is required to investigate the therapeutic or the neutraceutical implication of the lettuce cultivars.

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