A New Bistetrahydrofuran Acetogenin from the Roots of Annona salzmanii 1 Emerson F. Queiroz, † Franc ¸ ois Roblot,* ,† Andre ´ Cave ´, † Reynald Hocquemiller, † Laurent Serani, ‡ Olivier Lapre ´vote, ‡ and Marc ¸ al de Q. Paulo § Laboratoire de Pharmacognosie, U.R.A. 1843 CNRS (BIOCIS), Faculte ´ de Pharmacie, 92296 Cha ˆ tenay-Malabry, France, Laboratoire de Spectrome ´ trie de Masse, Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette, France, and Laboratory of Organic Chemistry, Department of Chemistry, University of Paraiba, 58000, Joa ˜ o Pessoa, Paraiba, Brazil Received November 2, 1998 A new bistetrahydrofuran acetogenin, salzmanin (1), was isolated from the MeOH extract of Annona salzmanii, in addition to the known compounds, squamocin, almunequin, bullatalicin, and annonacin. The structure of 1 was elucidated by spectroscopic methods, including LSIMS-MS technique, and confirmed by a chemical transformation. The cytotoxic activity of 1 and squamocin was investigated. The Annonaceous acetogenins are only encountered in a few members of the Annonaceae family. These polyketide- derived natural products have received much interest in recent years due to their significant antitumor, cytotoxic, antiparasitic, immunosuppressive, and insecticidal activi- ties. 2,3 In a continuation of studies on this family, we have investigated the acetogenins from the roots of Annona salzmanii D. C. (Annonaceae). 4 Alkaloid components have been previously reported from this plant. 5 The present study has led to the isolation and structure elucidation of salzmanin (1), a new bistetrahydrofuran (bis-THF) aceto- genin, together with the known squamocin, 6 almunequin, 7 bullatalicin, 8 and annonacin. 9 Results and Discussion Salzmanin (1) was isolated as a transparent oil from the MeOH extract of the roots by liquid-liquid partition followed by usual chromatographic methods including preparative HPLC. The structure was determined by 1 H and 13 C NMR (COSY, HOHAHA, HMBC, and HMQC), and MS (LSIMS-MS) on the native compound. The molecular weight of 1, established by LSIMS as 638 from the [M + Li] + ion observed at m/z 645, is in agreement with the molecular formula C 37 H 66 O 8 . A weak UV absorption at 208.0 nm, and a strong one at 1749 cm -1 in the IR spectrum, indicated the presence of an R,-unsaturated γ-lactone moiety, characteristic for acetogenins of subtype 1. 2,3 This structural feature was confirmed by typical resonances in the 1 H and 13 C NMR spectra (Table 1), also indicating the absence of OH group at C-4. 2,3 The presence of an adjacent bis-THF system was deduced from the 1 H NMR signals at δ 3.88 (2H), 3.79 (1H), and 3.75 (1H) for 1, assigned to four oxymethine protons, in agreement with their 13 C NMR signals at δ 83.2 (1C), 82.7 (2C), 81.7 (1C). 10 Two hydroxymethine groups flanking the bis-THF sys- tem were observed at δ 3.36 and 3.75 in the 1 H- 1 H COSY spectrum, and at δ 74.1 and 71.3 in the 13 C NMR spectrum. Two further oxymethine protons appeared at δ 3.52 in the 1 H NMR. Their 13 C NMR resonances at δ 71.5 and 71.6 were indicative of isolated hydroxy groups in the aliphatic chain. 11,12 The position of substituents on the aliphatic chain was further determined by MS. 2,3 The high-energy collision- induced dissociation (CID) spectrum of the [M + Li] + ion displayed the typical fragmentation pattern of lithiated acetogenins. 13 Two pairs of fragment ion peaks at m/z 221/ 291 and m/z 345/415 were assigned easily to fragmenta- tions across two adjacent THF rings (ions Y 1 -Y 2 and B 1 - B 2 respectively, according to Das and Lapre ´vote 13 ), indicating the position of the bis-THF system along the alkyl chain. The m/z values of these fragments accounted for the presence of two hydroxy groups between the THF and the terminal lactone and of two other hydroxy groups on the methyl-terminal side chain, their locations being deduced from careful scrutiny of the CID spectrum. Two series of fragment ion peaks were, indeed, attributed to charge- remote fragmentations of the alkyl chain from the [M + Li] + precursor ion at m/z 645. Among them, the diagnostic fragment ions at m/z 559 and 529 were indicative of a hydroxy group at the C-28 position. The location of the three remaining OH groups at C-12, C-15, and C-24 was obtained by a similar way. The relative stereochemistry around the bis-THF rings was determined by comparing the 1 H and 13 C NMR signals of 1 and the 1 H NMR data of its tetraacetate (2) (Table 1) with those of model compounds of known relative stereo- chemistry. 14,15 The comparison suggested that the relative configurations at C-15/C-16 and C-23/C-24 were different, according to the chemical shifts observed for H-15 or H-24 at δ 3.36 (threo) and 3.75 (erythro) for 1. To determine the relative configurations between C-12/ C-15 and C-24/C-28, the formaldehyde acetal derivatives (3, 4) were prepared from 1. 16 The derivative 3 shows an ion peak at m/z 651 [M + H] + in the CIMS (CH 4 + ) spectrum, in agreement with the molecular formula C 38 H 66 O 8 of a monoacetal derivative. The position of the acetal substituent was deduced from the fragment ions observed in the EIMS (Figure 1). The downfield shifts (δ 3.62 and 3.58) of two hydroxyme- thine protons (H-24 and H-28, respectively) and the ap- pearance of two doublets at δ 5.10 and 4.57 (J ) 7.4) in * To whom correspondence should be addressed. Tel.: 0033 (1) 46 83 5593. Fax: 0033 (1) 46 83 5399. † Laboratoire de Pharmacognosie. ‡ Laboratoire de Spectrome ´trie. § Laboratory of Organic Chemistry. 710 J. Nat. Prod. 1999, 62, 710-713 10.1021/np980482g CCC: $18.00 © 1999 American Chemical Society and American Society of Pharmacognosy Published on Web 04/07/1999