1. Ribosome-inactivating proteins were found in high amounts in one line of cells of Phytolacca americana (pokeweed) cultured in vitro and, in less quantity, in lines of Saponaria officinalis (soapwort) and of Zea mays (corn) cells. 2. The main ribosome-inactivating protein from pokeweed cells was purified to homogeneity. It is a protein with Mr 29,000 and basic pI, similar to the 'pokeweed antiviral protein' (PAP), a ribosome-inactivating protein from pokeweed leaves. We propose to call the pokeweed antiviral protein isolated from pokeweed cells PAP-C. 3. PAP-C inactivates ribosomes in a less-than-equimolar ratio, thus inhibiting protein synthesis by a rabbit reticulocyte lysate with an IC50 (concentration causing 50% inhibition) of 0.067 nM (2 ng/ml), and modifies rRNA in a manner apparently identical to that of ricin and other ribosome-inactivating proteins. It inhibits protein synthesis by intact cells with an IC50 of 0.7-3.4 microM, and is toxic to mice with an LD50 of 0.95 mg/kg.

Crude methanolic extracts from both root and cell cultures of Euphorbia calyptrata were investigated and found to be active on the CNS. An active fraction was isolated from the methanolic extract of suspension cultures; this possesses significant depressant activity on the CNS. When compared with the crude methanolic root extract, this fraction showed the presence of some common products, four of which were isolated and characterized as helioscopinolides A, C, D, and E. The pure products, administered intraperitoneally to mice, showed different activities on the CNS. Helioscopinolide C showed a clear depressant activity, helioscopinolide E a mild, short depressant effect, while helioscopinolides A and D had an opposite excitatory effect.

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

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