N-isobutyl-trans-2-trans-4-eicosadienamide and other alkaloids of fruits of Piper guineense

A novel alkaloid, N-isobutyl-trans-2-trans-4-eicosadienamide, has been isolated from the fruits of Piper guineense and fully characterized. The structure of the compound has been confirmed by an unambiguous synthesis of the tetrahydro derivative. The known alkaloid, δαβ-dihydropiperine has also been isolated and the position of the double bond in this compound confirmed by the use of an NMR shift reagent.     

Novel amide alkaloids from the roots of Piper guineense

Two novel amide alkaloids, wisanine and wisanidine, have been isolated from the petroleum-extract of the roots of Piper guineense, and found to be N-piperidyl-5 (2-methoxy-4,5-methylenedioxyphenyl)-trans-2-trans-4-pentadienamide and N-pyrrolidyl-5-(2-methoxy-4, 5-methylenedioxyphenyl)-trans-2-trans-4-pentadienamide respectively. The structure of wisanidine has been confirmed by synthesis. N-Isobutyl)-trans-2-trans-4-eicosadienamide, recently reported to be present in the fruits of the plant as well as Piperine and Δ^α,β-dihydropiperine have also been found to be major constituents of the roots.     

Total synthesis of sylvamide,A Piper alkamide

The structure, N-isobutyl-4,5-dihydroxy-2(E)-decenamide, for sylvamide is confirmed by its total synthesis. The erythro stereochemistry is also established by comparison of the properties of the natural and synthetic samples.     

An aromatic amide C-glycoside and a cyclitol derivative from stem barks of Piper guineense Schum and Thonn (Piperaceae)

Two new compounds, an aromatic amide C-glycoside, 4-C-β-D-glucopyranosyl-3,5-dihydroxy-2-methoxybenzamide (1) and a cyclitol derivative, 4-O-caffeoyl-2-C-methoxycarbonyl-1-C-methyl-2,3,6-trihydroxycyclohexanecarboxylic acid (2), were isolated from the methanol soluble extract of the stem barks of Piper guineense Schum and Thonn, together with four known quinic acids derivatives including 3-O-caffeoyl-1-methylquinic acid (3), 3-O-feruloylquinic acid (4), ethyl-4-O-feruloylquinate (5), and 5-caffeoylquinic acid (6). Their structures were established on the basis of detailed spectroscopic analysis. The radical scavenging activity of the isolates were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. Five of them were found to have significant radical scavenging activities, while compounds 2 and 3 displayed the highest activities with IC₅₀ values of 8.35 and 7.06 μM, respectively.     

Piplartine-dimer A,a new alkaloid from Piper tuberculatum

Piplartine-dimer A (1), a dimer of the known pyridone alkaloid piplartine, was isolated from root bark of Piper tuberculatum. It is accompanied by piplartine (3) and 3,4,5-trimethoxycinnamic acid.     

Two amides from Piper amalago

The hexane extracts of the roots of Piper amalago afforded two trans-cinnamoylamides, 2-methoxy-4,5-methylenedioxy-trans-cinnamoyl piperidide and pyrrolidide.     

A new benzoic acid derivative isolated from Piper cf. cumanense Kunth (Piperaceae)

New benzoic acid derivative (1), together with five known compounds has been isolated from the inflorescences of Piper cf. cumanense Kunth (Piperaceae). The structure was identified on basis of spectroscopic analysis and comparison with literature data. The compound (1) showed antifungal activity against Fusarium oxysporum f. sp. dianthi and Botrytis cinerea.     

Minor lignans of Piper clusii

Further investigations on the petrol extract of Piper clusii have afforded four more new lignans.These are 2S,3R,4R,2-ethoxy-3-(3,4,5-trimethoxyphenyl)methyl 4-(1,3-benzodioxol-5-yl) methyl tetrahydrofuranol; 3R,4R,bis-3,4-(3,4,5-trimethoxyphenyl) methyl tetrahydrofuran-2-one; 2R,3R,2-(7-methoxy-1,3-benzodioxol-5-yl) methyl 3-(3,4,5-trimethoxyphenyl)methyl butan-1,4-diol and 2R,3R,2-(1,3-benzodioxol-5-yl)methyl 3-(3,4,5-trimethoxyphenyl) methyl butan-1,4-diol. This is the first report of these compounds from a natural source.     

Floral development of dioecious species and trends of floral evolution in Piper sensu lato

The initiation of the floral parts (mainly stamens and carpels) is described for the four dioecious species of Piper: Piper polysyphorum C. DC, P. bavinum C. DC., P. pedicellatum C. DC., P. pubicatulum C. DC. The initiation order resembles that in the perfect flowers of some species, such as P. amalago. The carpels are initiated simultaneously, in most cases, as three primordia. In P. polysyphorum , carpel tips split into two lobes, so that finally a four- or five-lobed stigma will be formed when the ovary is fully developed. The staminodes (exactly, staminodial primordia) in the female flowers are initiated in the same order as the stamens in the male flowers and remain until the ovaries are enclosed. The unisexual flowers have stamens reduced to three or two. The reduction of stamen or staminode (staminodial primordium) number is accompanied by the change of their positions from opposite the carpels to alternate. After the initiation of the staminodes, or, exactly staminodial primordia, in the female flowers, the central part of the floral apex forms a ring meristem which is triangular. The carpel primordia (often three) are initiated on the three points of the ring meristem. The evolutionary trends of the flowers of Piper sensu lato are discussed.     

Chemical constituents of the Piper crocatum leaves and their chemotaxonomic significance

Chemical study of Piper crocatum leaves has led to isolation of a new megastigmane glucoside isomer (18), along with 23 known compounds including fifteen phenolic compounds (1–15), two monoterpenes (16 and 17), three sesquiterpenes (19–21), a phenolic amide glycoside (22), a neolignan (23), and a flavonoid C-glycoside (24). Structures of these compounds were identified via spectroscopic methods and compared with those reported in the literature. Seven compounds (7, 11, 13, 14, 17, 20, and 24) from the P. crocatum species and 17 others (1–6, 8–10, 12, 15–16, 18–19, and 21–23) from the Piper genus and Piperaceae family were isolated and reported for the first time. Furthermore, this study discusses chemotaxonomic relations between P. crocatum and other Piper species.