Assessment of Phytochemical and Biological Properties of Otostegia limbata (Benth.) Bioss. by Applying Various In Vitro Procedures

Abstract

Orosregia limbata (Benth.) Boiss. (Famil y: Lamiacae) is an important underex plored ethnomedicinal plant that has been used as antinflammatory, anti cancer and antibacterial herbal remedy previously. The present work was aimed to evaluate the anti ox idant, antimicrobial, an til eishmanial, antidi abetic and anti cancer prospective of O. limbatao Stem and leaf ex tracts prepared from wide ranging polarity sol vents were subjected to phytochemical and in v;lro assays to evaluate the most profi cient sol vent system and plant part for each bioacti vity. An array of colorimetric assays elaborating anti oxidant mechani sm was employed to profi le pl ant 's antioxi dant proficiency as well as overall phenolic and flavonoid content. Spec ific polyphenols were quantified by reverse phase HPLC anal ysis. Disc diffu sion method established pl ant' s antimicrobial and protein kinase inhibitory activ it y. Preliminary cytotoxicity was tested using brine shrimp lethality assay while anti proliferative acti vity against THP- I and Hep-G2 cell lines was detenni ned by 3-(4,5-dimethylthiazol-2-y l)-2,5- diphenyltetrazolium bromide (MIT) and sulforhodamine B (SRB) protocols respecti vely. Antileishmani al potential was assessed via MIT colorimetric method. Whereas a-amylase inhibit ion assay was adopted to in vestigate antid iabetic prospect. The highest amount of gall ic acid equ ivalent (GAE) phenol ic and quercetin equi valent (QE) fl avonoid content was obtained in methanol (MeH) ex tract of stem i.e., 53.29±1.33 ~ g GAE/mg ex tract and 28.64± l. l6 IJg QE/mg extract respecti vely. The results of HPLC quantifi ed signifi cant amoun ts of polyphenols i.e., catechin, gall ic acid, apigenin and rut in ranging from 0.31 ±45 to 12. IO±O.8 1 IJ glmg ex tract in various ex tracts. Among the stem samples, MeH ex tract showed maxim um ant ioxidant acti vity in temlS of DPPH free rad ical quenchi ng (ICso=34.5± 1.34 IJglml) while in case of leaf, it was observed highest in the methano l-ethyl acetate (MeH-EaC) ex tract (ICso=46.05± 1.39 IJglml). A substanti al antifungal activity was recorded in most of the non-polar and moderately pol ar stem and leaf ex tracts with MIC ranging between 100-6.25 pgldi sc. Moderate antibacterial acti vity was observed in both stem and leaf extracts (MIC= IOO-33.3 IJglml). Cytotoxici ty against brine shrimps categorized 2 1% of stem and 57% of leaf extracts as highly potent (LC50=50- IOO IJglml ). Signi ficant cytotoxicity against human leukemia (THP- l ) ceJl line was exhi bited by MeH-EaC stem and methanol-disti lled water (MeH-DWat) leaf extracts with IC50 values of 5 . 9±O . 4 3 ~g1m l and 3.46±O.25 IJglml respectively. Most promi sing anti proliferative vi act ivity agai nst Hep-G2 hepatoma cancer cell line was revealed by 46% extracts of O. limbata with ICso val ues ranging from OA4±OAS to 3.SS±0.67 )lglml. A negligib le hemolysis at concentration of 200 )lglml revealed the selective cytotoxicity agai nst cancer cell lines in comparison to normal body cells (RBCs). MeH-DWat and MeH extracts of stem and leaf showed conspicuous protein ki nase inhibitory acti vity (MIC= 12.5 Ilgldisc) whi le n-hexane (Nhex) and MeH-DWat extracts of stem and leaf revealed remarkab le antileishmanial acti vity (IC50=4.4S±0.4S and I.SO±O.23 Ilglml respectively). A noteworthy ant id iabet ic potential was recorded by chlorofonn (ChLr) stem and Nhex leaf extracts (ICso=33.1±O.S4 and 36.2±0.49 )lglml respectively). In concl usion, use of diverse polarity solvent system was observed to be a crucial variable in biological profi ling of O. limba/a and it can be envisaged as a novel source of natu ral anticancer, antilei shmanial, antifungal and antid iabetic compounds. Bioactivity guided isolation remains necessary to obtain lead compounds and detailed mechanistic study is recommended.