Uncaria rhynchophylla, alkaloids

Hirsutine (2-795), which belongs to the corynanthe subgroup of the indole alkaloids, was isolated from the plant Uncaria rhynchophylla MIQ and used for the preparation of the old Chinese folk medicine Kampo [397]. It is of pharmacological interest as it shows a strong inhibitory effect on the influenza A virus (subtype H3N2) with an EC50 = 0.40-0.57 pg ml. which is about 11- to 20-fold higher than that of the clinically used ribavirin [398]. 

The alkaloids hirsutine (1) and its 3or-epimer dihydrocorynantheine (2a) belong to the corynanthe group of indole alkaloids. They have been isolated from the plant Uncaria rhynchophylla MIQ, which was used for the preparation of the old Chinese folk medicine kampo . Nowadays, 1 and related compounds attract great attention in medicine because of their growth inhibition of the influenza A subtype H3N2 virus. With an EC50 value of 0.40-0.57 ig/mL 1 has shown itself to be 10-20 times more active than the clinically used drug ribavirine (3).1,2 Furthermore, 1 is known for its antihypertensive and antiarrhythmic activity.3... 

Tietze s synthesis of hirsutene 141, an alkaloid from Uncaria rhynchophylla used in Chinese traditional medicine and with promising activity against influenza viruses, uses many chemose-lective reactions of which we shall discuss just three - one at the start, one in the middle, and one at the end of the synthesis.25... 

Oxindole and indole alkaloids corynoxeine, hirsutine, and hirsuteine from uncaria Uncaria rhynchophylla Miq.) as the main compounds of the extract destabilize the formation of Ap aggregates [185]. They also have a neuropro-tective effect and inhibit glutamate-induced neurotoxicity in the cells of the cerebellum [186]. 

Indole alkaloids hirsutine and hirsuteine are the major constituents of the root bark of Uncaria rhynchophylla. Along with these, minor indole alkaloids cor-... 

From the leaves of Uncaria rhynchophylla, a glycoindole alkaloid, rhyn-chophine, has been isolated along with vallesiachotamine, vincoside lactam, and strictosamide (2). 

Aimi N, Shito T, Fukushima K, Itai Y, Aoyama C, Kunisawa K, Sakai S, Haginiwa J, Yamasaki K 1982 Studies on plants containing indole alkaloid glycosides and other constituents of the leaves of Uncaria rhynchophylla Miq. Chem Pharm Bull 30 4046 - 4051... 

Haginiwa J, Sakai S, Aimi N, Yamanaka E, Shinma N 1973 Studies of plants containing indole alkaloids. (2) On the alkaloids of Uncaria rhynchophylla Miq. Yakugaku Zasshi 93 448-452... 

Numerous bioactive alkaloids have been isolated from Uncaria [35—47], but two species yielded a considerable number of active compounds U. rhynchophylla and U. tomentosa. 

This is also identified as Chotoko in Japanese traditional medicine. It is composed of several Uncaria spp. including U. rhynchophylla, U. macrophylla, U. sinensis, and U. sessilifructus however, U. rhynchophylla is a major component. Gou-teng is commonly used for its sedative, antispasmodic, analgesic, anticonvulsive, hypertensive, antiepileptic, and antiviral properties [12]. The cmde drug is used to relieve headaches and dizziness caused by hypertension and infantile nervous disorders. Recent studies have evaluated that the active ingredients of Gou-teng are the alkaloids of U. rhynchophylla [12]. 

The phytochemical studies of Uncaria spp. have begun in early 1900s [11]. Rhynchophylline (1.1) is one of the earliest reported compounds from the hooks of U. rhynchophylla [11]. Latter studies on these plants reported over 150 compounds that belong to mainly three classes of compounds (i) alkaloids, (ii) terpenoids, and (iii) flavonoids. In addition, several unusual structures were also identified [6]. Major emphasis of this chapter is on the occurrence of these compounds among various species, their structural diversity and pharmacological activities. 

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