Inhibition of HIV-1 enzymes, antioxidant and anti-inflammatory activities of Plectranthus barbatus

Abstract

Ethnopharmacological relevancePlectranthus barbatus is widely used in African countries as an herbal remedy to manage HIV/AIDS and related conditions. Aim of the studyTo investigate the HIV-1 inhibitory, anti-inflammatory and antioxidant properties of P. barbatus and thereby provide empirical evidence for the apparent anecdotal success of the extracts. Materials and methodsEthanolic extract of P. barbatus's leaves was screened against two HIV-1 enzymes; protease (PR) and reverse transcriptase (RT). Cytotoxicity of the extract was determined through measuring tetrazolium dye uptake of peripheral blood mononuclear cells (PBMCs) and the TZM-bl cell line. Confirmatory assays for cytotoxicity were performed using flow cytometry and real-time cell electronic sensing (RT-CES). The free radical scavenging activity of the extract was investigated with 2,2-diphenyl-1-picrylhydrazyl while the anti-inflammatory properties of the plant extract were investigated using a Th1/Th2/Th17 cytometric bead array technique. The extract exhibited strong antioxidant activity with an IC 50 of 16 µg/ml and reduced the production of pro-inflammatory cytokines indicating anti-inflammatory potential. ConclusionThis is the first demonstration of the in vitro anti HIV-1 potential of P. barbatus including direct activity as well as through the stimulation of protective immune and inflammation responses. The low cytotoxicity of the extract is also in agreement with the vast anecdotal use of this plant in treating various ailments with no reported side-effects.

In vitro anti-HIV and antioxidant activity of Hoodia gordonii (Apocynaceae), a commercial plant product

“…1) against HIV-1 Reverse transcriptase (RT) with IC 50 values of 73.55 ± 0.04 and 69.81 ± 9.45 μg/mL, respectively (Table 2). Doxorubicin, a known RT inhibitor [16], was used as a positive control and inhibited HIV RT by 68 % at 25 μg/mL (IC 50  < 25 μg/mL). Both extracts also demonstrated inhibitory activity against HIV protease (PR) with IC 50 values of 97.29 ± 0.01 and 63.76 ± 9.01 μg/mL for ethanol and ethyl acetate extracts, respectively.…”

“…Plant material (108.3 g) was macerated at room temperature in 1 L of ethanol for 48 h. The filtrate was then concentrated under reduced pressure using a rotary evaporator and half of the residue obtained was further extracted in ethyl acetate to exclude highly polar tannins which are regarded as non-specific enzyme inhibitors [16]. The extracts obtained were dried in a fume hood and stored at room temperature until further use.…”

“…The free radical scavenging activity of the extract was evaluated using a modified method previously described [16]. Various concentrations of H. gordonii extracts were mixed with 90 μM DPPH.…”

Cellular injury evidenced by impedance technology and infrared microspectroscopy

“…The crude extract of the leaves was prepared and kindly donated by Dr. T. P. Kapewangolo, Department of Biochemistry, University of Pretoria. The plant extraction procedure was done as previously described [20].…”

“…This technique successfully characterized the type of cellular responses of importance in our research group [19,20] as well as others [16,[21][22][23].…”