HomoLycorine Lycorine

Figure 2. Proposed AA biosynthetic pathways. Three major groups of AA (para-ortho para-para , ortho-para ) are represented along with the nine proposed AA types norbelladine-, galanthamine-, crinine-, narciclasine-, haemanthamine-, montanine-, homolycorine-, lycorine-, and narcissidine-type (shaded gray). Broken arrow indicates more than one step.

Amaryllidaceae Leucojum vernum Lycorine Homolycorine 2-O-acetyllycorine Leucovernine Acetylleucoverine N-demethylgalanthamine... 

Lycoris aura (L Her.) Herb. L. longituba Y. Han et Fan L. radiata (L Her.) Herb. Shi Suan (Amaryllis) (rhizome) Galanthamine, lycoremine, lycorine, lycoramine, lycorenine, tazettine, pseudolycorine, dihydrolycorine, homolycorine, lycoricidine, lycoricidinol.33 As a cholinesterase inhibitor, lower blood pressure, stimulate secretion from the pituitary gland, increase natidiuretic hormone secretion. 

The pyrrolo[de]phenanthridine alkaloids (lycorine type) and the 2-benzopirano-[3,4-g]indole alkaloids (homolycorine type) both originate from an ortho-para phenol-oxidative coupling (Fig. 5). 

Narcissus tazetta L. is also cultivated as an ornamental plant and for the production of volatile oil. From this species a number of alkaloids were isolated [10-12, 14] which showed great interest because of their effective antitumoral [173] and antiviral activities, particularly against choriomeningitis virus [174]. Lycorine, homolycorine and tazettine were... 

Absolute configurations were first assigned to alkaloids of this section both by chemical transformations to compounds in the lycorine series where Mills rule had been applied and by Klyne s modification of the Hudson lactone rule. This extension states that lactones possessing the absolute configuration of XLVII are more positive in molecular rotation than derivatives in which the lactone ring is opened. If this rule is applicable to the alkaloids of this section, the conversion of homolycorine (XLVIII [M]d -f-268°) to tetrahydrohomolycorine (XLIX [M]d —322°) requires that homolycorine and tetrahydrohomolycorine have the absolute configurations shown in XLVIII and XLIX. These assign-... 

These alkaloids are among the most abundant of the bases derived from the [2]benzopyrano[3,4gf]indole nucleus in the Amaryllidaceae family, and the title of this section is derived from this fact. Lycorenine (LXVI) was one of the first Amaryllidaceae alkaloids to be studied and a summary of the chemical degradations leading to this structure (without stereochemical implications) has been given in Volumes II and VI. Lycorenine and the corresponding lactone, homolycorine (LXVII), not only serve as the reference alkaloids of the group for recent spectroscopic studies but also provides a chemical correlation with the lycorine-type alkaloids. Several important chemical interconversions are given below. 

The bulbs of Hippeastrum ananuca have been shown to contain lycorine, homolycorine, and the rare alkaloid maritidine (1). Lycorine has also been isolated for the first time from the rhizomes of Curculigo orchioides and from the leaves of Ungernia tadshicorum maritidine is a constituent of Zephyranthes robusta and of Z. sulphurea and an X-ray crystallographic study of the alkaloid has been carried out. Two new alkaloids, hippeastidine (2) and 17-epi-homolycorine (3), were obtained from Hippeastrum ananuca and their structures were established by X-ray analysis. 

The large number of structurally diverse Amaryllidaceae alkaloids are classified mainly into nine skeleton types, for which the representative alkaloids are norbelladine, lycorine, homolycorine, crinine, hemanthamine, narciclasine, tazettine, montanine, and galanthamine (Fig. 1). With the aim of unifying the numbering system of the different skeleton types, Ghosal s model will be used in this review (20). 

The alkaloids of the lycorine and homolycorine groups are, on the whole, the most common alkaloids in this genus. Lycorine (1), galanthine (7), and pluviine (11) (lycorine type) and homolycorine (26) and lycorenine (35) (homolycorine type) are particularly frequent, lycorine being the most abundant. The presence of these alkaloids is very significant in the sections Narcissus (mainly lycorine type). Pseudonarcissi (mainly homolycorine type), and Tazettae of the wild species, and in the Divisions 1, 2, and 4 of cultivars. 

The alkaloids of the homolycorine series, formed by a restructuring of lycorine-type alkaloids, are absent from some tribes of the Amaryllidaceae, such as the Amaryllideae or Hemantheae (44). For that reason, the presence of these alkaloids is a distinctive feature of the Narcisseae tribe. Moreover, all the Narcissus alkaloids of the homolycorine series display a B/C ring junction with a cis stereochemistry. An exceptional homolycorine-type alkaloid is dubiusine (33), which has an unusual hydroxybutyryl substituent (72). 

It is well established that profiles of alkaloids vary with time, location, and developmental stage. In many instances, the site of biosynthesis is restricted to a single organ, but accumulation of the corresponding products can be detected in several other plant tissues. Long-distance transport must take place in these instances. There are only a few data on the ontogenic variations and distribution of alkaloids in species of the Amaryllidaceae family, and some results have been obtained in Narcissus species, such as N. assoanus (with only lycorine-type alkaloids) or N. confusus (with alkaloids of the homolycorine, hemanthamine, tazettine, and galanthamine types) 84,87). 

Skeleton types LY, lycorine FIL, homolycorine HT, hemanthamine TZ, tazettine NC, narcielasine MN, montanine GA, galanthamine OA, other alkaloids. Alkaloid names see Tables I-VII. 

In Egypt, mixture from roots of Amaryllis belladonna and Cltvia miniata were used to treat and prevent infection of wounds such as insect and snake bites. The anti-microbial activities are achieved by virtue of eertain types of AAs namely lycorine, homolycorine, haemanthamine and tazettine present in the root mixture [10, 15, 19]. 

Figure 8. Biosynthesis of o-p alkaloids such as lycorine, homolycorine and narcissidine. Broken arrow represents more than one biochemical reaction. Abbreviations R, reduction O, oxidation NMT, N-methylation OMT, O-methylation.

Synthesis of alkaloids of the first structural type [such as lycorine (8), norpluviine (9), lycorenine (10), and homolycorine (11)] in various daffodil varieties may occur as indicated (Fig. 33.4). Radioactively labeled norbellidine (5) is incorporated into norpluviine (9). 

On the basis of recent phytochemistry investigation about Amaryllidaceae alkaloids, anew 12-type classificatimi, including (1) norbelladine type, (2) lycorine type, (3) homolycorine type, (4) crinine and haemanthamine types, (5) tazettine type, (6) montanine type, (7) pUcamine type, (8) graciline type, (9) galanthindole type, (10) galanthamine type, (11) phenanthridone and phenanthridine types, and (12) other minor species populations, are deduced according to their ring systems. Representative structures for each type of Amaryllidaceae alkaloids are shown in Tables 17.2-17.13. 

The conversion of norpluviine 261 into homolycorine 3 has been validated via the benzylic oxidation at C6 position followed by B-ring opening to form an amino aldehyde with a free hydroxyl group, which gives alkaloid lycorenine 54 after 77,0-methylation [112]. Finally, a subsequent oxidation produces homolycorine 3 (Scheme 17.5). Recently, the transformation from lycorine-type skeleton into homolycorine-type alkaloid has been experimentally demonstrated through a total synthesis of alkaloid clivonine 76 [113]. 

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