Indian Journal of Experimental Biology VoL 39, December 2001, pp. 1302-1304

Antidepressant activity of conjugates of the St.John's wort, Linn.: An experimental study

A V Muruganandam & S K Bhattacharya* Department of Pharmacology, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221 005, India and S Ghosal Drug Research and Deve lopment Centre, 1078, Jessore Road, Calcutta 700 028, India Received 11 November 2000; revised 26 July 2001

Nine extracts of H. petforatwn, containing hyperfo rin in conjugated forms, but devoid of free hyperforin and adhyper­ forin, were subj ected to screening using the forced swim test (FST). The observed activity was compared with that of SJW extracts containing hyperforin and adhyperforin (in free form). Results indicate that hyperforin conjugates exhibit significant antidepressant acti vity as evidenced by the reduced immobility period in the FST in rats.

Extracts of Hypericum perforatum Linn. (St.John's ministered (50 mg/kg/day) orally for three days in wort, SJW) have shown significant antidepressant 0 .3% CMC suspension. The experiment was per­ activity in both expenmenta. 1 1· 2 an d c l'mtca . l stu d'te s 3 . formed after 45 min of the final administration of the Earli er, hypericin, a napthodiantherene derivative pre­ drugs or the vehicle. sent in SJW, was thought to be the active constituent SJW Extracts- In a typical experiment, the dried responsible for the antidepressant activit/. However, overground parts of the H. peiforatum (SJW), col­ in later studies the earlier results could not be con­ lected from Northern India, were extracted continu­ firmed5. More recently, hyperforin, a prenylated ously with aqueous acetone (Soxhlet, 12h). The sol­ derivative, present in the plant, has vent was removed from the extract under vacuum. A been projected as primarily responsible for the antide­ portion of the dried extract was accurately weighed, 6 9 pressant activity of SJW . . In the present study, SJW dispersed in water and further extracted with chloro­ collected from Northern parts of India were examined form. The chloroform soluble fraction was dried and for their hyperforin and adhyperforin contents by redissolved in methanol (1 mg/ml) and subjected (20 HPLC, usi111g authentic markers. Interestingly, in five ~-tl) to HPLC analysis (WATERS ASSOCIATES of the nine extracts examined (SJW 1-5) hyperforin HPLC assembly equiped with PDA detector; column : and adhyperforin were vicariously represented by the reverse phase RP-Cl8 (Novapak 3.9xl50 mm); elu­ corresponding conjugates. The remaining four ex­ ent: acetonitrile - water- phosphoric acid (80:20:01); tracts (SJW 6-9) contained hyperforin, adhyperforin flow rate : 1.2 mVmin; pressure 1500 psi; scanning at and also hyperforin conjugates (as minor entities). In 270 nm) using hyperforin and adhyperforin as mark­ thi s study, the contribution of hyperforin conjugates, ers to eliminate the possibility of their occurrence in if any, on the antidepressant activity of SJW was the extract. Likewise, the HPLC spectrum of hyper­ studied on forced swim test (FST). FST was selected forin conjugates exhibited absence of hyperforin and for thi s study since its relevance has been demon­ adhyperforin. strated with a large number of clinically used antide­ 10 The nature of the hyperforin conjugates was estab­ pressants . li shed by comprehensive spectroscopic analyses (UY, Animals-Albino rats (CF strain) of either sex. 1 HNMR) and crucial chemical transformation of hy- were housed in colony cages maintained at 22° ± I °C . 10 perf onn . in a 12 hr darkilight cycle. The rats had free access to Forced swim test- The rats were pl aced in a water and standard lab chow. SJW extracts were ad- chambers (45x20 em) containing water up to 25 em *Correspondent author: Fax No. 0542-316068 (25° ± 2°C), so that it could not touch the bottom of . E. mai l:salil @banaras.ernet.in the cylinder with its hind limb or tai l, or climb over NOTES 1303

Table !- Percentage abundances of hyperforin, adhyperforin· and its conjugates in SJW extracts and their effect on Forced Swim Test (FST) in rats [Values are mean± SE, n=6]

Groups % Relative Abundance FST Hyperforin Adhyperforin Hyperforin conjugates Immobility period (sec)

Vehicle 115.2 ± 9.37 SJW I 16.31 46.0 ± 4.25•• SJW2 06.32 60.0 ± 5.51 aa SJW3 09.64 42.6 ± 6.14aa SJW4 14.31 49.8 ± 6.14aa SJW 5 12.42 69.0 ± 4.45 .. SJW6 4.60 4.15 00.53 52.0 ± 5.78aa SJW 7 0.33 0.09 02.48 41.8 ± 5.02aa SJW 8 1.70 0.92 05.2 1 48.4 ± 4.93aa SJW9 0.53 0.31 08.42 39.4 ± 2.32aa 62.3 ± 3.81 aa

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