Journal of Ethnopharmacology 61 (1998) 135 – 142
Neuromuscular blocking activity of methanolic extract of Piper
sarmentosum leaves in the rat phrenic nerve-hemidiaphragm
preparation
Wibool Ridtitid *, Wattana Rattanaprom, Peerarat Thaina, Somsmorn Chittrakarn,
Methi Sunbhanich
Department of Pharmacology, Faculty of Science, P.O. Box 3, Prince of Songkla Uniersity, Hat Yai 90112, Thailand
Received 15 December 1997; received in revised form 26 January 1998; accepted 10 February 1998
Abstract
Methanolic extract of Piper sarmentosum Roxb. (Piperaceae) leaves was studied for the neuromuscular blocking
activity in rat phrenic nerve-hemidiaphragm preparations. The plant extract, at concentrations of 3.2, 4.0, 4.8 and 6.4
mg/ml, exhibited an initially transient increase in twitch tension which was followed by a marked dose-related
neurally-evoked twitch depression. The neuromuscular blocking effect produced by the plant extract was compared
with d -tubocurarine (dTC) and succinylcholine (SCh). The EC
50
for neurally-evoked twitch depression of the extract,
dTC and SCh was 4.07 mg/ml, 1.1 M and 15 M, respectively. The neurally-evoked twitch depression produced by
the extract was partially antagonized by tetraethylammonium (TEA) but not by neostigmine (NS). These findings
suggested that the plant extract possessed a marked neuromuscular blocking activity at the neuromuscular junction
and a possible mechanism which was likely to inhibit neurotransmitter (acetylcholine) release at the presynaptic
terminal. © 1998 Elsevier Science Ireland Ltd. All rights reserved.
Keywords: Piper sarmentosum; Methanolic extract of Piper sarmentosum; Neuromuscular blocking activity
1. Introduction
Thailand is endowed with a great diversity of
indigenous medicinal plant species, and the Thais
have a long tradition of using medicinal herbs and
plants in folklore medicine. However, many of the
claimed curative properties have not been scien-
tifically proven (Mahidol, 1996). Among the
plants, Piper sarmentosum Roxb. (syn: Piper ros -
tratum Roxb.), a terrestrial herb of the piperaceae
family, 1–2 feet high, jointed at the nodes, with
thin, dark green and ovate leaves, has been
known locally as ‘Cha-plu’ and is widely dis-
tributed throughout Thailand (Suvatti, 1978). In * Corresponding author
0378-8741/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved.
PII S0378-8741(98)00025-7