Dereplication of Bioactive Spirostane Saponins from Agave macroacantha

A dereplication strategy using UPLC-QTOF/MSE, the HMAI method, and NMR spectroscopy led to the identification of five main steroidal saponins (1-5), including three previously unknown compounds named macroacanthosides A-C (3-5), in a bioactive fraction of Agave macroacantha. The major saponins were isolated, and some of them together with the saponin-rich fraction were then evaluated for phytotoxicity on a standard target species, Lactuca sativa. The inhibition values exhibited by the pure compounds were confirmed to be in agreement with the phytotoxicity of the saponin-rich fraction, which suggests that the saponin fraction could be applied successfully as an agrochemical without undergoing any further costly and/or time-consuming purification processes. The NMR data of the pure compounds as well as of those corresponding to the same compounds in the fraction were comparable, which indicated that the main saponins could be identified by means of this replication workflow and that no standards are required

Unusual C,O-Fused Glycosylapigenins from Serjania marginata Leaves

A phytochemical study of a Serjania marginata leaf extract with antiulcer activity afforded 15 compounds, including the new 3-O-α-L-arabinopyranosyl(1→3)-α-Lrhamnopyranosyl(1→2)[β-D-glucopyranosyl(1→4)]-α-Larabinopyranosyloleanolic acid (1) and 7,5″-anhydroapigenin 8-C-α-(2,6-dideoxy-5-hydroxy-ribo-hexopyranosyl)-4′-O-β-D-glucopyranoside (4). The structures of the new compounds were determined by spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry, and chemical methods. Compound 4 is a C-hexopyranosylapigenin with an unusual cyclic ether linkage between C-5″ and C-7 of apigenin. The isolated proanthocyanidins have high antioxidant activities, and these compounds are probably responsible for the gastroprotective effect of the extract

Agave Steroidal Saponins as Potential Bioherbicides

Agave saponins are a valuable resource for the prospective development of new forms of agrochemicals. The extraction method was optimized and applied to 17 Agave species. Thirteen saponin fractions (SFs) were assayed on wheat etiolated coleoptiles, and analysed using UPLC-QTOFMSE, NMR spectroscopy and the HMBC method for aglycone identification (HMAI). Six SFs were assayed on standard target species (STS) and weeds. The new extraction method reduces costs to obtain SFs with the same activity. The tested SFs assayed on etiolated wheat coleoptiles that belong to the subgenus Agave were among those with the highest activity levels. The combination of HMAI together with UPLC-MS allowed the identification of 20 aglycones in the SFs, and no isolation or hydrolysis of the saponins was required. A Principal Component Analysis (PCA) showed that for the active SFs the structural key would be the length of their sugar chain. The presence of a carbonyl group at C-12 implied an enhancement in phytotoxic activity. Six SFs were assayed on seeds, and no activity on Solanum lycopersicum (tomato) was observed; however, good activity profiles were obtained on weed E. crus-galli (IC50 < 80 ppm), better than the commercial herbicide Logran®. These findings represent a possible lead for the development of natural herbicides through the use of saponins of subgenus Agave species

Isolation and Structural Determination of Triterpenoid Glycosides from the Aerial Parts of Alsike Clover (Trifolium hybridum L.)

Five azukisapogenol glycosides (1−5) have been isolated from the aerial parts of alsike clover (Trifolium hybridum L.), and their structures were elucidated by combined spectroscopic, spectrometric (1D and 2D NMR; HRESIMS, ESI−MS/MS), and chemical methods. Three of them are new compounds and were identified as 3-O-[-α-L-arabinopyranosyl(1→2)]-β-Dglucuronopyranosyl azukisapogenol (1), 3-O-[-β-D-glucuronopyranosyl(1→2)-β-D-glucuronopyranosyl]-29-O-β-D-glucopyranosyl azukisapogenol (2), and 3-O-[-α-L-arabinopyranosyl(1→2)-β-D-glucuronopyranosyl]-29-O-β-D-glucopyranosyl azukisapogenol (3). The remaining two (4, 5) are known compounds but have not been previously described as saponins constituents of the genus Trifolium. Also, azukisapogenol is reported here as a triterpenoid aglycone for the first time in this genus. Finally, the main chemotaxonomic features that may be recognized as specific of Trifolium species were discussed

Bioactive steroidal saponins from Agave offoyana flowers

Bioguided studies of flowers of Agave offoyana allowed the isolation of five steroidal saponins never described previously, Magueyosides A–E (1–5), along with six known steroidal saponins (6–11). The structures of compounds were determined as (25R)-spirost-5-en-2a,3b-diol-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-( 1-4)-O-b-D-galactopyranoside} (1), (25R)-spirost-5-en-2a,3b-diol-12-one 3-O-{b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-(1-4)-O-b-D galactopyranoside} (2), (25R)-spirost-5-en-2a,3b,12b-triol 3-O-{b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]- O-b-D-glucopyranosyl-(1-4)-O-b-D-galactopyranoside} (3), (25R)-5a-spirostan-2a,3b-diol-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-(1-4)-O-b-D-galactopyranoside} (4), and (25R)-5a-spirostan-2a,3b-diol-9(11)-en-12-one 3-O-{b-D-xylopyranosyl-(1-3)-O-b-D-glucopyranosyl-(1-2)-O-[b-D-xylopyranosyl-(1-3)]-O-b-D-glucopyranosyl-( 1-4)-O-b-D-galactopyranoside} (5), by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The bioactivities of the isolated compounds on the standard target species Lactuca sativa were evaluated. A dosedependent phytotoxicity and low dose stimulation were observed

Phytotoxic steroidal saponins from Agave offoyana leaves

A bioassay-guided fractionation of Agave offoyana leaves led to the isolation of five steroidal saponins (1–5) along with six known saponins (6–11). The compounds were identified as (25R)-spirost-5-en-2α,3β-diol-12-one 3-O-{α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (1), (25R)-spirost-5-en-3β-ol-12-one 3-O-{α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glu copyranosyl-(1→4)-O-β-D-galactopyranoside} (2), (25R)-spirost-5-en-3β-ol-12-one 3-O-{β-D-xylopyrano syl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyranosyl-(1→4)-O-β -D-galactopyranoside} (3), (25R)-26-O-β-D-glucopyranosylfurost-5-en-3β,22α,26-triol-12-one 3-O- {α-L-rhamnopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β-D-glucopyrano syl-(1→4)-O-β-D-galactopyranoside} (4) and (25R)-26-O-β-D-glucopyranosylfurost-5-en-3β,22α,26-triol- 12-one 3-O-{β-D-xylopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-O-[β-D-xylopyranosyl-(1→3)]-O-β- D-glucopyranosyl-(1→4)-O-β-D-galactopyranoside} (5) by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The phytotoxicity of the isolated compounds on the standard target species Lactuca sativa was evaluated

Triterpenoid saponins from the aerial parts of Trifolium argutum Sol. and their phytotoxic evaluation

Four triterpenoid saponins (1–4) were isolated from the aerial parts of Trifolium argutum Sol. (sharptooth clover) and their structures were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry and chemical methods. Two of them are new compounds, characterized as 3-O-[α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyra- nosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (1) and 3-O-[β-D-galactopyranosyl-(1→2)- β-D-glucuronopyranosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (2). The occurrence of 3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (melilotigenin) in its natural form is reported for the first time as a triterpenoid aglycone within Trifolium species. The phytotoxicity of compounds was evaluated on four STS at concentration 1 μM to 333 mM. Compound 1 was the most active, showing more than 60% inhibition on the root growth of L. sativa at the higher dose, with IC50 (254.1 μM) lower than that of Logran1 (492.6 μM), a commercial herbicide used as positive control. The structure–activity relationships indicated that both aglycones and glycosidic parts may influence the phytotoxicity of saponins