ALKALOIDS OF THE AFRICAN RAUWOLFIA SPECIES OF THE SUB-SECTION OPHIOXYLANTHUS
ALKALOIDS OF THE AFRICAN RAUWOLFIA SPECIES OF THE SUB-SECTION OPHIOXYLANTHUS
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Date
1978-11
Authors
Bamidele, Akinyemi Akinloye
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Abstract
The a l k a l o i d s of t h e Rauwolfia s p e c i e s have been reviewed and
s p e c t r o s c o p i c methods of i d e n t i f i c a t i o n d i s c u s s e d.
D e t a i l e d phytochemical i n v e s t i g a t i o n s have "been c a r r i e d out on
t h e two s p e c i e s of t h e s e c t i o n Ophioxylanthus of P i c h o n ' s c l a s s i f i c a t i on
of t h e genus Rauwolfia. In a l l , n i n e t y a l k a l o i d s were i s o l a t e d and
t h e i r s t r u c t u r e s e l u c i d a t e d.
R. v o l k e n s i i s t a p f root y i e l d e d t w e n t y - s i x a l k a l o i d s i n c l u d i ng
two new compounds, t e t r a p h y l l i c i n e - 1 7 - O - a c e t y l and r a u v o l c i n i n e . The
stem b a r k gave s e v e n t e e n a l k a l o i d s i n c l u d i n g t h e new a l k a l o id
p r e - p e r a k i n e . Thirteen a l k a l o i d s were i s o l a t e d from t h e l e a v e s , four
of which are new n a t u r a l p r o d u c t s i . e . m e t h o x y - p l e i o e a r p a m i n e , methoxyp
l e i o c a r p a m i n e 2 : 7 d i h y d r o , methoxy-pleioearpamine N-oxide and
v o l k e n s i n e . The a l k a l o i d p l e i o c a r p a m i n e and i t s d e r i v a t i v e s have not
p r e v i o u s l y been i s o l a t e d from any Rauwolfia s p e c i e s.
l\- o r e o g i t o n Mgf. root y i e l d e d t h i r t e e n a l k a l o i d s of which t h r ee
have not been p r e v i o u s l y r e p o r t e d i n t h e p l a n t . The l e a v e s y i e l d ed
t w e n t y - o n e a l k a l o i d s i n c l u d i n g f i v e new ones , akuammiline-5-formyl,
o r e o g U, akuammiline 2 - d i h y d r o , d e a c e t y l akuammiline 2/4 - d i h y d r o and
an i m p o r t a n t b i o g e n e t i c i n t e r m e d i a t e a l k a l o i d a d i r u b i n e a c e t a t e 19 : 20
dehydro.
The i n t e r - r e l a t i o n s h i p of t h e i s o l a t e d a l k a l o i d s has been d i s c u s s ed
and b i o s y n t h e t i c pathways proposed. The evidence o b t a i n e d concerning the
a l k a l o i d s of t h e s e c t i o n Ophioxylanthus s p e c i e s has been used t o r e l a te
t h e s e c t i o n chemotaxonomically to t h e o t h e r African Rauwolfia s e c t i o n s and
t h e c l o s e l y r e l a t e d genus Cabucala.
Description
A Thesis submitted
to the University of Bradford for the degree
of Doctor of Philosophy
Postgraduate School of Studies in Pharmacy
University of Bradford
November, 1978
Keywords
ALKALOIDS,, AFRICAN,, RAUWOLFIA,, SPECIES,, SUB-SECTION,, OPHIOXYLANTHUS.