Alkaloids of the Asclepiadaceae

The structures of the major alkaloids of Stephanotis japonica were reported earlier.8 Two minor alkaloids, stephanthraniline B (7a) and dihydrogagaminin 

---

Cynanchum vincetoxicum (L.) Pers. contains traces of an alkaloid vincetene, which shows an interesting relationship to the phenanthroindolizidines found in Tylophora and other genera of the Asclepiadaceae. Spectroscopic study has shown vincetene to be the benzopyrroloisoquinoline derivative (2), and this structure has been confirmed by synthesis of the racemic dihydro-desoxy-deriva-tive (3).2... 

Steroidal Alkaloids of the Apocynaceae, Buxaceae, Asclepiadaceae, and of the Salamandra-Phyllobates Group... 

Furoquinoline Alkaloids.—Well-known furoquinoline alkaloids have been identified for the first time in twelve species of the Rutaceae (see the Table 2.5.8,9,11—13,15,16 on p an(j rare trimethoxydictamnine halfordinine (1 R1 = R2 = R3 = OMe) has been obtained from Araliopsis tabouensis2 and from Teclea verdoorniana.12 The isolation of y-fagarine and skimmianine from Tylophora asthmatica (Asclepiadaceae)14 and skimmianine from Datura stramonium (Solanaceae)4 is of considerable taxonomic interest. 

Tylophorine (1) and its analogs, the phenanthroindolizidine alkaloids also referred to as tylophora alkaloids, have been isolated primarily from plants of the family Asclepiadaceae [13-16], Fig. (1), including members of the genus Tylophora, Vincetoxicum, Pergularia, Cynanchum, but also from Hypoestes verticillaris (Acanthaceae) [17], Cryptocarya phyllostemmon (Lauraceae) [18], Ficus hispida and F. septica (Moraceae) [2, 19]. TTie isolations of these alkaloids are summarized in Table 1. The most significant phenanthroindolizidine alkaloids are tylophorine (1), tylocrebrine (2), antofine (3), and tylophorinine (4), Fig. (2). 

Septicine (866), the prototypical alkaloid in this group, is a seco variant of the more populous phenanthroindolizidine class of alkaloids, of which tylophorine (867) and antofme (868) are commonly encountered examples. All fte known analogs of septicine are metabolites of the unrelated genera Cryptocarya (Lauraceae), Ficus (Moraceae), and Tylophora (Asclepiadaceae). In addition to Ihe previously described alkaloids 8a-hydroxysepticine (869) and hispidine (870) (7), seven new members of the family have been isolated (Table II and Fig. 16). 

The aerial parts of Cynanchum vincetoxicum (L.) Pers. (Asclepiadaceae) contain three phenanthroindolizidine alkaloids, which have been shown to be tylophorine (34), 7-demethoxytylophorine (Alkaloid A, 35), and 7-demethoxy-demethyltylophorine (Alkaloid C, 36). The trimethoxy-base (35) has also been isolated, together with two unidentified alkaloids, from the dried roots of the same plant,and from Vincetoxicum officinale Moench., in which it occurs along with tylophorine. The early work on this trimethoxy-base indicated that it was either (35) or the 3,6,7-trimethoxy isomer, but this latter possibility has now been excluded. The n.m.r. spectrum did not allow a distinction to be made between (35) and the 3,6,7-trimethoxy analogue, hence the alkaloid was oxidised by mercuric acetate, and the immonium salt so obtained was... 

A cytotoxic alkaloid from Boehmeria cylindrica (Urticaceae), active in cell cultures against Eagle s K.B. carcinoma of the nasopharynx, but inactive against sarcoma 180, adenocarcinoma 755, L-1210 leukaemia, and Walker carcinosarcoma, was identified as cryptopleurine (61) (67) is a close relative of tylocrebrine (68), from Tylophora crebrifolia (Asclepiadaceae), whose high activity against lymphoid leukaemia L-1210 in mice had been observed. ... 

Thus, noteworthy is the sap or juice from members of the genus Asclepias, or milkweed, of the family Asclepiadaceae, as indicated elsewhere, and which contains alkaloids (e.g., Hoffman, 1999, p. 505). Traditionally, such tissue-destroying chemicals as phenol (carbolic acid) have been used to selectively remove warts (although... 

The order Gentianales (Apocynaceae, Gentianaceae, Lo-ganiaceae, Rubiaceae, and Theligonaceae) contains normal iridoid monoterpenes and secoiridoids, as well as iridoid-derived alkaloids in families other than the Asclepiadaceae. Multiple types of alkaloids are found in the Apocynaceae (indole and steroidal types), the Loganiaceae, and Rubiaceae (emetine, quinine, and indole types). 

Cryptolepine (47) from the roots of Cryptolepis sanguin-olenta (Asclepiadaceae), is highly active against Plasmodium falciparum. The in vitro IC50 value for this alkaloid is 0.03 JLg/ml, compared to 0.07 xg/ml for chloroquine, a common antimalarial drug (Phillipson et al., 1993). Extracts of the roots of the plant also are used to treat patients in some Southeast Asian countries. 

Minor alkaloid from the leaves of Tylophora asthmatica and from T. tanakae (Asclepiadaceae). Cryst. (CH2Cl2/MeOH). Mp 212-214° (198-203° dec.), [a ... 

The distribution of the complex indole alkaloids in plants will not be discussed except to point out that they occur most frequently in the family Apocynaceae and to a lesser extent in the Asclepiadaceae, Loganiaceae and Rubiaceae and it is worth remembering that these families stand close together in the phylogenetic charts of the taxonomists. The simpler indole derivatives are of much wider distribution but likewise confined largely to the Dicotyledons. 

Cryptolepine is an indoloquinolone alkaloid isolated from Cryptolepis sangui-nolenta (Asclepiadaceae) which is widely used traditionally in folklore medicine in many parts of the world for the management, and/or treatment of a plethora of human ailments, including diabetes mellitus. This compound... 

Dcemia extensa (Asclepiadaceae). Dutta and Ghosh were unable to confirm the presence of an alkaloid in spite of previous records to the contrary. ((1) J. Amer. Pharm. Assoc., 1947, 36, 250 Gupta, Roy and Dutta, Ind. J. Med. Res., 1946, 34, 181. (2) Dymoek, Warden and Hooper, Pharmacographia Indica,... 

Asclepias fruticosa L. [lubetjane, milkweed] (Asclepiadaceae) stem bark concoction is used in the treatment of asthma. The stem bark contains alkaloids, flavonoids, polyphenols, saponins and steroids (15). The aerial parts contain cardenolides (55). The powdered leaf is used as a snuff for the treatment of pulmonary tuberculosis, producing violent and prolonged sneezing in the process (28). 

Struct, unknown. Mol. formula not reported. Co-occurs with Cryptolepine and Quindoline (see 10/f-Indolo[3,2-6]quinoline, 1-00134). Could possibly be identical with the recently isolated Isocryptolepine. Alkaloid from roots of Cryptolepis sanguinolenta (Asclepiadaceae). Mp >300°. 

The latter alkaloid is a violet base obtained from Cryptolepis species (Asclepiadaceae) which with selenium gave quindoline which had already been prepared 45 years before. An efficient biogenetic type synthesis of cryptolepine was from indoxyl and o-methylamino benzaldehyde in weakly acidic medium. 

---