Inhibition of Neutrophil Function by Barleria Lupulina lindl and Clinacanthus nutans (burm. F.) Lindau

Abstract

Barleria lupulina Lindl and Clinacanthus nutans (Burm. f.) Lindau, both

belonging to the family Acantaceae, have been widely used in Thai folkore medicine

as an anti-inflammatory agents and for the treatment of insect bite, allergic response

and herpes infection. However, the mechanisms underlying their activities in these

treatments have never been reported. In the present study, extracts from the leaves and

twigs of B. lupulina and C. nutans were investigated for their inhibitory activities on

neutrophil functions, including neutrophil chemotaxis, superoxide anion generation

(SAG) and degranulation. It was found that B. lupulina (10-1000 μg/ml) and C. nutans

(10-1000 μg/ml) inhibited fMLP-induced neutrophil chemotaxis in a

concentration-dependent manner with IC50 = 8.0 ± 2.2 μg/ml and IC50 = 11.9 ± 2.2

μg/ml, respectively. Both B. lupulina and C. nutans (10-1000 μg/ml) caused a

concentration-related inhibition of fMLP-induced SAG with IC50 for B. lupulina was

42.4 ± 10.7 μg/ml and for C. nutans 62.2 ± 9.2 μg/ml. These concentrations of both

herbs also inhibited fMLP-induced elastase release in a concentration-dendent manner

with IC50 = 145.7 ± 15.1 μg/ml and IC50 = 86.1 ± 18.5 μg/ml, respectively. The results

also showed the inhibitory effects of B. lupulina (10-1000 μg/ml) and C. nutans (10-

1000 μg/ml) on neutrophil MPO production, giving IC50 = 64.1 ± 10.2 μg/ml and IC50

= 48.2 ± 11.1 μg/ml, respectively. These findings suggest that inhibition of neutrophil

activation by these herbs may be attributed, in part, to their anti-inflammatory

activities.