The acetogenins are a class of potent bioactive compounds found in various plant species in the Annonaceae.* 1 Motivated by their promising potential as new antitumor drugs,1 we have now investigated the bioactive leaves of Rollinia mucosa (Jacq.) Baill. (Annonaceae). Some initial results have been reported elsewhere.2 Herein, we report the isolation, absolute structure determination, and bioactivity of mucocin (1, Figure 1). The previously known acetogenins are usually characterized (among other features) by their bearing one to three tetrahydrofuran (THF) rings.1 1 is the first annonaceous acetogenin to be reported that bears a hydroxylated tetrahydropyran (THP) ring along with a THF ring. This finding adds a new skeletal type to the family of annonaceous acetogenins.The isolation of 1 was guided by the brine shrimp lethality test (BST)3 45using repetitive open column and HPLC chromatography to separate the partitioned ethanol extract.2,4 The molecular formula of 1 was determined as CsvHeeOg by HRFABMS (MH+, m/z found 639.4828, caled 639.4836). A DEPT experiment revealed the presence of two methyl, 10 methine, and two quaternary carbons (some methylene carbon peaks overlapped at <5 29.5). The planar structure was established by means of COSY, EIMS, and EIMS of its TMS derivative (la, Figure 1). The cross peak corresponding to H-20/23 was successfully observed in the double-relayed COSY spectrum of 1. The existence of the methylated ,/9-unsaturated y-lactone with a 4-OH was confirmed by comparing the and 13C NMR data (Table 1) with those of known annonaceous acetogenins.1The relative stereochemistry of 1 was established as follows. Applying Bom's rule,5 the <3 value of H-16 indicated a three relationship at C-15/16. The configurational assignment of the THF ring as trans was suggested by the close match of the ,3C NMR data (from C-12 to C-16) with those of synthetic model 3 Purdue University. * Missouri Botanical Garden.(1) For recent reviews on annonaceous acetogenins, see: (a) Rupprecht,

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The Annonaceous acetogenins represent a class of compounds with diverse bioactivities, including promising cytotoxicites. These are due, at least in part, to inhibition of complex I in the oxidative phosphorylation pathway in mitochondria. Fourteen Annonaceous acetogenins were tested in a rat liver mitochondrial oxygen uptake assay to probe additional structure-activity relationships. In this subcellular assay, the activity of non-adjacent bis-THF ring acetogenins depends on the distance between the two THF rings; the activity decreases to that of a mono-THF ring acetogenin if the distance is too long. When one THF ring is replaced with a tetrahydropyran ring, the activity remains comparable. The configuration of the THF ring, in mono ring compounds, seems to be more important than stereochemical differences in the rings of adjacent bis-THF ring compounds. Bullatacin, an adjacent bis-THF ring acetogenin, was used as a standard compound in every run to normalize the data.

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Sixteen withanolides isolated from Iochroma gesnerioides (Kunth) Miers (Solanaceae) have been assessed for their activities as ecdysteroid agonists and antagonists. None of the compounds showed any agonistic activity, but several showed significant antagonistic activity. With a 20‐hydroxyecdysone concentration of 5 times 10−8 M, the ED50 values for 2,3‐dihydro‐3ξ‐methoxywithaferin A, 2,3‐dihydro‐3ξ‐methoxywithacnistine, 2,3‐dihydro‐3ξ‐methoxyiochromolide and 2,3‐dihydro‐3ξ‐hydroxyξwithacnistine are 3.5 times 10−5 M, 1 times 10−5 M, 5 times 10−6 M and 2.5 times 10−6 M, respectively.