The chemical constituents and biological activities of the essential oil and the extracts from leaves of Gynura divaricata (L.) DC. growing in Thailand

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 values of 5.79, 47.44 and 17.65 µg/mL, respectively and had a MIC of 50 μg/mL against Mycobacterium tuberculosis H37Ra. Cubenol had an IC50 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

Phytochemical screening, phenolic and flavonoid contents, antioxidant and cytotoxic activities of Graptophyllum pictum (L.) Griff

The phytochemical screening of the leaves of Graptophyllum pictum (L.) Griff. was carried out using the standard procedures which revealed the presence of flavonoids, steroids, tannins, coumarins, saponins, anthraquinones, phenolics and sugars. In vitro antioxidant activity, total phenolic and total flavonoid contents of four different fractions from the ethanolic leave extract of G. pictum (L.) Griff. were determined using spectrophotometric methods. The ethyl acetate fraction showed the highest total phenolic content (102.57 ± 0.19 mg gallic acid equivalent/g) and the hexane fraction contained the highest flavonoid (28.21 ± 0.04 mg quercetin equivalent/g). The ethyl acetate fraction also exhibited the highest antioxidant capacities in the DPPH radical scavenging assay with the IC50 value of 0.78 ± 0.01 mg/mL and was found 69.19 ± 0.73 mg trolox equivalent capacity/g and 48.04 ± 0.49 mg ascorbic acid equivalent capacity/g when investigating by the ABTS radical scavenging assay. Moreover, the hexane, the ethyl acetate and the aqueous fractions exhibited significant cytotoxicity against MCF-7 cell lines with IC50 values of 38.66, 26.01 and 20.41 μg/mL, respectively. All fractions were non-cytotoxic against Vero cells. The results of all experiments suggest that the leaves of G. pictum (L.) Griff. can be a natural candidate for rich source of antioxidants for further chemical investigation

Concise synthesis of (-)-steviamine and analogues and their glycosidase inhibitory activities

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)

The chemical constituents and the cytotoxicity, antioxidant and antibacterial activities of the essential oil of Graptophyllum pictum (L.) Griff

The essential oil from the leaves of Graptophyllum pictum (L.) Griff. was isolated by hydrodistillation and its chemical constituents were investigated by a combination of gas chromatographic (GC-FID) and gas chromatography-mass spectrometric (GC-MS) analysis. Fourteen compounds, comprising 95.0 % of the gas chromatographical oil, were identified. The major constituents were phytol (75.7 %), n-nonacosane (6.5 %) and hexahydrofarnesyl acetone (2.6 %). The oil showed significant cytotoxicity against KB (epidermoid carcinoma of oral cavity), NCI-H187 (small cell lung carcinoma) and Vero cell lines with IC50 values of 27.04, 25.27 and 26.52 µg/mL, respectively. The antioxidant activity of the oil was determined using the ABTS radical cation scavenging assay. The oil had less antioxidant activity than the controls, trolox and ascorbic acid. In a disc diffusion assay the oil exhibited antibacterial activity against S. aureus and E. coli with MIC values of 11.75 and 35.25 µg/disc, respectively

Synthesis of α-propargylglycinates using the borono-mannich reaction with pinacol allenylboronate and potassium allenyltrifluoroborate

The three component borono-Mannich reactions of ethyl glyoxylate, primary or secondary amines and pinacol allenylboronate or potassium allenyltrifluoroborate are highly regioselective and give α-propargylglycinates. The (S)-N-tert-butylsulfinyl imine of ethyl glyoxylate underwent an indium chloride catalyzed addition reaction with allenyl potassium trifluoroborate in a highly regioselective and diastereoselective manner to give ethyl (S)-α-propargylglycinate after N-deprotection in 97 % ee

Total synthesis of hyacinthacines B3, B4, and B 5 and purported hyacinthacine B7, 7-epi-hyacinthacine B7, and 7a-epi-hyacinthacine B3 from a common precursor

The total synthesis of hyacinthacines B3, B4, and B5 and purported hyacinthacine B7, 7-epi-hyacinthacine B7, and 7a-epi-hyacinthacine B3 from a common anti-1,2-amino alcohol precursor is described. These syntheses confirmed that the proposed structures and absolute configurations of hyacinthacines B3, B4, and B5 were correct and disclosed that the proposed structure of hyacinthacine B7 was incorrect. Our synthetic and spectroscopic studies suggest that the natural hyacinthacines B5 and B7 are the same compounds; however, without access to authentic samples this cannot be unequivocally proven