Alfredo Ortega’s research while affiliated with National Autonomous University of Mexico and other places

Phytochemical investigation of the leaves and flowers from Salvia hirsuta led to the isolation of the five microphyllane-type diterpenoids (1–5), and two flavones (6–7). Hirsutolides constituted new diterpenoids containing a 5-hydroxyfuran-2(5H)-one and were isolated as an epimeric mixture at C-3 and C-15. The structures of the isolated compounds were established through the analysis of their NMR spectroscopic and MS spectrometric data; and confirmed by single-crystal X-ray diffraction studies. Cytotoxic and MDR modulatory activities of compounds 1–5 were determined.

Both DNA barcoding and phylogenetic data of the studied botanical material suggested the existence a new population of Galphimia glauca. Their leaves afforded three new nor-3,4-seco-friedelanes named galphimines M-O, together with known galphimines D, E, G, and I. Galphimines M and N possess bicyclic orthoacetates which are the first examples of orthoesters found in the Malpighiaceae family, while galphimine O has a 27,20-δ-lactone moiety. The structures elucidation followed from spectroscopic means and the absolute configuration followed from single crystal X-ray diffraction analyses. Tests for antibacterial and antifungal activities of galphimines N and M showed no promising effects.

The bark of the roots of Piscidia carthagenensis afforded the known insecticides rotenone (1) and millettone (2), as well as the new rotenoid piscicartone (3). The structure of 3 followed from nuclear magnetic resonance studies, while its absolute configuration (AC) was determined by vibrational circular dichroism (VCD) measurements in comparison with discrete Fourier transform B3LYP/DGDZVPcalculated spectra using the CompareVOA software. In addition, the AC of 1 and 2 was verified using the same VCD methodology.

Nine terpenoids were isolated from the leaves and flowers of Salvia amarissima, including a new acylated diterpenoid glucoside, amarisolide F (1), a new neo-clerodane diterpenoid, amarissinin D (2), which was isolated as an acetyl derivative (2a), and four known diterpenoids. The structure of amarisolide F (1) was elucidated by NMR and MS data analyses, as well as its methanolysis products 7 and 8, which also constituted new diterpenoids, named amarissinin E and 8-epi-amarissinin E, respectively. The absolute configuration of compound 7 was established by single-crystal X-ray diffraction. The cytotoxicity and anti-MDR effect of 1 in three phenotypes of the MCF-7 cell lines were assayed. Compound 1 was 2-3.6-fold more active than amarissinins A (3) and B (4), but several orders of magnitude less active than teotihuacanin (6) and reserpine. © 2018 American Chemical Society and American Society of Pharmacognosy.

An account of the difficulties to determine the absolute configuration (AC) of guaiaretic acid (1a), using contemporary methodology, is described in commemoration of the century of its structure elucidation. In fact, the herein studied molecule was the derived diacetate 1b, since the natural lignan slowly decomposes upon manipulation. Single crystal X-ray diffraction of 1b demonstrated the structure, but calculation of Flack and Hooft parameters to know the AC was unsuccessful since the crystals were triclinic, P-1, which is a centro-symmetric space group. In turn, manual band to band comparison of experimental and DFT B3LYP/DGDZVP calculated VCD spectra of 1b allowed ascertaining its AC, although automatic comparison using the CompareVOA software was not very successful. This behavior is associated to the fact that the studied molecule has a sole stereogenic center located on the acyclic portion of a carbon chain possessing two quite similar substituents. The behavior is discussed in relation to cases where the molecular flexibility also generates a very large number of conformers.

Eleven neo-clerodane diterpenoids (1–11) including the new analogues 1, 2, and 10, and 3′,5,6,7-tetrahydroxy-4′-methoxyflavone (12) were isolated from the aerial parts of Salvia polystachya. Polystachyne G (1) and 15-epi-polystachyne G (2) were isolated as an epimeric mixture, containing a 5-hydroxyfuran-2(5H)-one unit in the side chain at C-12 of the neo-clerodane framework. Polystachyne H (10) contains a 1(10),2-diene moiety and a tertiary C-4 hydroxy group. The structures of these compounds were established by analysis of their NMR spectroscopic and MS spectrometric data. The absolute configurations of compounds 3, 4, and 10 were determined through single-crystal X-ray diffraction analysis. The antibacterial, antifungal, and phytotoxic activities of the diterpenoids were determined. In addition, the stimulatory effect of the expression of extracellular matrix components of nine of the isolates (1–8 and 11) was assayed. Compounds 1–4, 8, and 11 increased the expression of the genes codifying for type I, type III, and type V collagens and for elastin.

NMR and single crystal X-ray diffraction analysis of seven clerodanes from Mexican Salvia species was performed. We focused on clerodanes with tertiary hydroxyl group at C-4, C-8, and C-10, in which the establishment of absolute configuration around these chiral centers is nontrivial and the ¹³C NMR signals can be misassigned. In addition, the analysis by ¹H NMR in aprotic solvent allowed us to establish a common pattern that correlates the chemical shift with the position of the hydroxyl groups, which constitute a good methodology for future structural elucidation of these kinds of compounds. The obtained data allowed us to establish the absolute configuration of five of these diterpenes and the structural revision of salvimicrophyllin D (7).

The structure of the dimeric eudesmanolide hydroxy-bis-dihydrofarinosin (1) from Encelia farinosa followed after contrasting their 1H and 13C NMR spectra with those of encelin (6), hydroxy-bis-dihydroencelin (3), and farinosin (4). Structure 1 was verified by single crystal X-ray diffraction analysis, which further provided the streochemistry of the hydroxy group at C-4. Comparison of the experimental vibrational circular dichroism spectrum of its derived diacetate 2 with that calculated by DFT provided the absolute configuration, which resulted the same as that of its biogenetic precursor 4. Evaluation of several chemical shits differences between the two eudesmanolide fragments of 1 and 3 allows also ascertaining the yet not reported absolute configuration of the C-4 stereogenic center of 3.

The authors regret. 3. Results and discussion. Page 5, 1st column, 2nd paragraph. Revised to: “In the ¹H NMR spectra, two signals of vinylic protons at δH 6.07 (d, J = 10.4 Hz) and 5.83 (dd, J = 10.4, 3.7 Hz) appeared, assigned to H-1 and H-2 by the COSY correlations between them. In the ¹³C NMR spectra, two signals for oxygenated carbons at δC 75.9 and 77.4 were assigned to C-10 and C-4 respectively, taking into account their HMBC correlations between H-1 and H-2 with C-10, and from H-2, H2-3 and H2-19 with C-4. Comparison of this NMR data with those described for the hydroxyclerodane: infuscatin (6, Fig. 1)¹⁹ indicated that 3 differs from 6 by the absence of a hydroxyl group at C-8.” The authors would like to apologise for any inconvenience caused.