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Four new diterpenoids, helioscopinolides F (2), H (4), I (5), and L (6), were isolated from three different cultured cell lines of Euphorbia calyptrata var. involucrata. Helioscopinolide B (1) and jolkinolide E (3), previously found in Euphorbia helioscopia and Euphorbia jolkini, respectively, were also isolated from the same cultures. Structures were identified by spectroscopic methods.

Inhibitory effects by addition of aqueous extracts of soy flour to an active Briggs-Rauscher mixture are reported. The effect consists of an immediate cessation of oscillations, but, after some time, the oscillatory behavior is regenerated with amplitude and frequency different from those observed in a reference mixture. The inhibition time depends linearly on the concentration of substances contained in the extract in a wide range of concentration. The inhibitory effects are due to the high free-radical scavenging activity of substances contained in the soy flour. Two preponderant products contained in the soy flour extract were identified and characterized as malonyldaidzin and malonylgenistin. The antioxidant activity of these isoflavones contained in the extracts was determined on the basis of the inhibition time. A qualitative mechanistic explanation of the inhibitory effects is given. Our findings are decisive indirect evidence of involvement and important role played by HOO . radicals in establishing oscillations in the Briggs-Rauscher (BR) system. The linear relationship between the inhibition time and the whole-mass concentration of antioxidant contained in soy extracts added to a BR mixture is an indication of the possibility to develop and implement an analytical procedure for monitoring the activity of antioxidant scavengers of free radicals based on the oscillating Briggs-Rauscher reaction.1. Introduction. ± As stated by Furrow and Noyes [1], the most dramatic oscillating reaction in solution is probably that discovered by Briggs and Rauscher [2], now referred to as the BR reaction. When appropriate amounts of H 2 O 2 , acidic iodate, manganous salt, malonic acid (MA), and starch indicator are mixed in aqueous solution, the system repeats the sequence colorless 3 yellow 3 blue several times.The mechanism of the BR reaction is quite complex; a skeleton mechanism, proposed in 1982 by Noyes and Furrow [3], reproduces some of the basic features of the oscillations in the system in closed reactors (batch conditions). At the same time, De Kepper and Epstein [4] developed a qualitatively similar mechanism that, taking into account flow terms, is able to model, besides oscillations, a variety of phenomena that appear in continuously stirred tank reactors (open conditions).The main intermediates in these mechanisms are: iodine, iodide ion, the oxyiodine species HOI, HOIO, and IO . 2 , and the hydroperoxyl radical HOO . . It is to be noted that IO .2 and HOO . radicals were not detected in BR mixtures: their presence and the important role they play in the onset of oscillations were proposed in analogy with the well-established mechanism for the Belousov-Zhabotinsky (BZ) reaction [5] and with a mechanism proposed for the Bray-Liebhafsky (BL) reaction [6].In a qualitative study, Franz [7] found that the addition of a crumbled superoxide dismutase pellet (health food, 2000 SOD units per pellet) to an actively reacting BR mixture caused an immediate cessation of oscillations (initial concentrations in the

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hSTRACT.-~rcduction of alkaloids with both canthin-6-one and P-carboline structure by Adantbur altissima cell cultures is reported. Besides canthin-6-one (l), l-methoxycanthin-6-one (2), canthin-6-one-3-oxide 0, 1-methoxycanthin-6-one-3-oxide (8), l-hydroxycanthin-6-one (3), 5-hydroxycanthin-6-one (6), P-carboline-1-propionic-acid (ll), and 4-methoxy-Pcarboline-I-carboxylic acid methylester (lo), three new alkaloids are described. These are 2-hydroxycanthin-6-one (4), 4-hydroxycanthin-6-one (5), and 4,5-dihydrocanthin-6-one (9).Ailanthus altissima Swingle (Simaroubaceae) is known to be a producer of indole alkaloids and has been extensively studied (1-4). These alkaloids belong to the class of either the simple P-carboline or the more complex canthin-6-one derivatives. The literature has recently reported (5) cell cultures of A. altissima that produced canthin-6-one (1) and 1-methoxycanthin-6-one (2), which are the two most abundant alkaloids in the intact plant.We investigated the production of some minor alkaloids whose presence had been suspected during a previous study undertaken in order to clarify the different steps of their biosynthesis (6). Eleven alkaloids were identified and isolated in satisfactory yields from a batch of 50 liters of cell suspension cultures ofA. altissima. Besides the main alkaloids l and 2, cell cultures produced their corresponding 3-oxides, 7 and 8, respectively, as well as P-carboline-1-propionic acid (ll), 4-methoxy-P-carboline-l-carboxylic acid methylester (lo), 5-hydroxycanthin-6-one (6) previously found in A. altissima (1,2,4), and 1-hydroxycanthin-6-one (3) found in Ailanthus giraldii (7). Furthermore, the following three alkaloids never before found in nature, 2-hydroxycanthin-6-one (4), 4-hydroxycanthin-6-one (5), and 4,5-dihydrocanthin-6-one (9), have been extracted. In spite of the predominant alkaloid canthin-6-one (1) produced in the amount of 300 Fglml of cell suspension, each of the new compounds 4,5, and 9 represent 0.3% of the total alkaloids, and their production is 2 pg/ml or less. RESULTS AND DISCUSSIONIn order to obtain a good amount of crude alkaloids and to identify all the alkaloids present in it, a batch of about 50 liters of cell suspension culture was prepared by pooling 900 Erlenmeyer flask cultures. Cells only were extracted as reported in the Experimental section, the medium being discarded because of its negligible content in alkaloids and high concentration of nutrients. The toluene extract of the cells was loaded on a silica gel column in toluene and eluted with increasing amounts of EtOAc. By this method pure 1 and 2 were obtained, while alkaloids 2,7,8, and 10 required further purification. Compound 9 submitted to eims showed a molecular ion at mlz 222, corresponding to a dihydrocanthin-6-one. The fragmentation pattern was similar to that