I. INTRODUCTION
Secondary metabolites isolated from natural sources, such as plants, lichens, fungi, and marine organisms, constitute an important source of potential pharmaceutical compounds. These materials are usually characterized by spectroscopic and chromatographic techniques. Since polymorphism is an important solid-state phenomenon among pharmaceuticals, X-ray powder diffraction techniques are particularly suitable for characterizing the nature of the crystalline phase, which would be of potential pharmaceutical interest. Perhaps because of the low yields obtained in the process of isolating the secondary metabolites, X-ray powder diffraction techniques are seldom used to characterize these materials. However, with the modern instrumentation having high-intensity sources and more sensitive detectors, a more extensive use of powder diffraction might be possible.
In this contribution, the X-ray powder diffraction data of ambroperuvin (Figure 1), 4α-hydroxy-6β-acetoxy-2βH(3βH)-epoxy-5βMe,7αH,8βH,10αH-pseudoguai-11(13)-en-12,8-olide(C17H22O6) is presented. This compound is a new pseudoguaianolide isolated from the aerial parts of Ambrosia peruviana Willd. (Asteraceae), a plant common in Lagunillas, Mérida state, Venezuela. Allelopathic activity has been reported for A. peruviana (Anaya and del Amo, Reference Anaya and del Amo1978). It is widely used for the treatment of skin spots, varicose veins, scars, and menstrual problems, among other conditions, in Venezuela and in other South American countries (Roth and Lindorf, Reference Roth and Lindorf2002).
Figure 1. Molecular diagram for ambroperuvin (C17H22O6).
The determination of the crystal structure of ambroperuvin was carried out from single-crystal data and is being reported elsewhere. In this report, the X-ray powder diffraction data of this material are presented.
II. EXPERIMENTAL
A. Sample preparation
Plant materials (leaves, stems, and inflorescence) of A. peruviana Willd. were collected in San Juan de Lagunillas, Mérida, Venezuela. The plant material was air-dried, ground, and subjected to an exhaustive extraction procedure with acetone. Subsequent extractions with hexane-EtOAc, EtOAc-MeOH, and hexane:dichloromethane mixtures produced a crude product, which was purified via preparative thin layer chromatography. Preliminary characterization of the material was carried out by Fourier transform infrared (FT-IR) on a KBr pellet using a Perkin-Elmer 1600 spectrometer at room temperature. The melting point of this compound was determined with an electro-thermal apparatus.
B. Powder diffraction data collection
A small portion of the title compound was gently ground in an agate mortar and dusted on top of a zero-background specimen holder. The powder diffraction data were collected using the θ-θ geometry at room temperature on a Siemens D5005 diffractometer equipped with a sample spinner, a graphite diffracted beam monochromator, a scintillation detector, and a long fine-focus Cu tube running at 40 kV and 30 mA. The data were collected over the angular range from 5° to 50° (2θ) with a step size of 0.02° (2θ) and a counting time of 80 s step−1.
III. RESULTS AND DISCUSSION
The FT-IR spectrum obtained was consistent with the functional groups present in the molecule. The melting point determined was 195–197 °C.
The indexing of the pattern recorded was successfully carried out with DICVOL14 (Louër and Boultif, Reference Louër and Boultif2014). The resulting orthorhombic unit cell was very similar to the cell obtained from the single-crystal study. The analysis of the entire pattern carried out with the program AIDS*NBS (Mighell et al., Reference Mighell, Hubbard and Stalick1981) led to a unit cell with parameters: a = 15.999(6) Å, b = 11.263(2) Å, c = 9.112(2) Å; V = 1642.0(5) Å3. The de Wolff (Reference de Wolff1968) and Smith and Snyder (Reference Smith and Snyder1979) figures of merit obtained were M 20 = 16.6; F 30 = 24.3 (0.0158, 78). The powder diffraction data are presented in Table I. Space group analysis using the program DAjust (Vallcorba et al., Reference Vallcorba, Rius, Frontera, Peral and Miravitlles2012) suggested space group P212121 as the most likely candidate. This result agrees with the single-crystal structure determination performed on this compound. The fitting of the whole pattern with the Le Bail algorithm implemented in FULLPROF (Rodriguez-Carvajal, Reference Rodriguez-Carvajal2001), accounts for all the diffraction maxima recorded (see Figure 2).
Figure 2. (Color online) The Le Bail profile fitting of the recorded X-ray powder diffraction pattern of ambroperuvin (C17H22O6).
Table I. X-ray powder diffraction data of ambroperuvin (C17H22O6).
SUPPLEMENTARY MATERIAL
The supplementary material for this article can be found at https://doi.org/10.1017/S0885715617000604.
ACKNOWLEDGEMENTS
The work carried out at Universidad de Los Andes is supported by Grant LAB-97000821 from FONACIT.
