Exploring the Anti-Acne Potential of Impepho [Helichrysum odoratissimum (L.) Sweet] to Combat Cutibacterium acnes Virulence

Abstract

The Gram-positive bacterium Cutibacterium acnes (previously Propionibacterium acnes), plays an important role in the pathogenesis and progression of the dermatological skin disorder acne vulgaris. The methanolic extract of Helichrysum odoratissimum (L.) Sweet (HO-MeOH) was investigated for its ability to target bacterial growth and pathogenic virulence factors associated with acne progression. The gas chromatography-mass spectrometry (GC-MS) analysis of HO-MeOH identified a-humulene (3.94%), acurcumene (3.74%), and caryophyllene (8.12%) as major constituents, which correlated with previous reports of other Helichrysum species. The HO-MeOH extract exhibited potent antimicrobial activity against C. acnes (ATCC 6919) with a minimum inhibitory concentration (MIC) of 7.81 µg/ml. It enhanced the antimicrobial activity of benzoyl peroxide (BPO). The extract showed high specificity against C. acnes cell aggregation at sub-inhibitory concentrations, preventing biofilm formation. Mature C. acnes biofilms were disrupted at a sub-inhibitory concentration of 3.91 µg/ml. At 100 µg/ml, HO-MeOH reduced interleukin-1a (IL-1a) cytokine levels in C. acnes-induced human keratinocytes (HaCaT) by 11.08%, highlighting its potential as a comedolytic agent for the treatment of comedonal acne. The extract exhibited a 50% inhibitory concentration (IC 50 ) of 157.50 µg/ ml against lipase enzyme activity, an enzyme responsible for sebum degradation, ultimately causing inflammation. The extract's anti-inflammatory activity was tested against various targets associated with inflammatory activation by the bacterium. The extract inhibited pro-inflammatory cytokine levels of IL-8 by 48.31% when compared to C. acnes-induced HaCaT cells at 7.81 µg/ml. It exhibited cyclooxygenase-II (COX-II) enzyme inhibition with an IC 50 of 22.87 µg/ml. Intracellular nitric oxide (NO) was inhibited by 40.39% at 7.81 µg/ml when compared with NO production in lipopolysaccharide (LPS)induced RAW264.7 cells. The intracellular NO inhibition was potentially due to the 2.14 fold reduction of inducible nitric oxide synthase (iNOS) gene expression. The HO-MeOH extract exhibited an IC 50 of 145.45 µg/ml against virulent hyaluronidase enzyme activity, Frontiers in Pharmacology | www.frontiersin.org January 2020 | Volume 10 | Article 1559 1 which is responsible for hyaluronan degradation and scar formation. This study provides scientific validation for the traditional use of H. odoratissimum as an ointment for pimples, not only due to its ability to control C. acnes proliferation but also due to its inhibitory activity on various targets associated with bacterial virulence leading to acne progression.

The Activity of Gold Nanoparticles Synthesized Using Helichrysum odoratissimum Against Cutibacterium acnes Biofilms

“…The results confirm that observed in the study by De Canha et al (2020) where even the nanoparticles show better inhibition of Cutibacterium acnes adhesion to the 96-well plate rather than disruption of the mature biofilms. The phenolic content of the highest tested concentration (25% v/v) was used to convert the minimum biofilm inhibitory concentration (MBIC 50 ) from % v/v to μg/mL of extract equivalents.…”

“…The synthesis of gold nanoparticles using both the dried plant material and the methanol extract of Helichrysum odoratissimum resulted in the reduction of the gold salt. The use of H. odoratissimum in the nanoparticle form exhibited similar anti-biofilm activity when compared to the biological activity of the methanol extract as previously reported by De Canha et al (2020) . The formation of nanoparticles with plant extracts or dried plant material result in several shapes, sizes and therefore explained the varied functionality.…”

“…The anti-adhesion activity of the HO-MeOH + GA AuNPs was significantly better than the HO-MeOH − GA variation. The activity of HO-MeOH against the prevention of biofilm formation by targeting bacterial cell adhesion was demonstrated in a previous study (De Canha et al, 2020). It is possible the phytochemical constituents responsible for the anti-adhesion activity, are also those responsible for the reduction of the gold salt and the formation and stabilization of the nanoparticles.…”

“…In this study the antibacterial and anti-biofilm activity of nanoparticles coated with phytochemicals found in both an aqueous decoction of the powdered aerial plant material and methanolic extract of H. odoratissimum were investigated against the acne causing bacterium C. acnes . The study aimed to determine whether the AuNPs synthesized using H. odoratissimum would show similar antimicrobial and anti-biofilm activity when compared to that of the extract alone, which was previously reported by De Canha et al (2020) .…”

“…To successfully compare whether the activity of the nanoparticles was better than those of the HO-MeOH alone [previously published in De Canha et al (2020) ] the total phenolic content of the synthesized nanoparticles was determined using the Folin Cioalteau technique as described by Basma et al (2011) with modifications. The standard curves were prepared using the HO-MeOH (with and without gum arabic) and the aqueous decoction (with and without gum arabic) as described in section “Synthesis of gold nanoparticles (AuNPs)” to calculate the extract equivalents in the synthesized nanoparticles.…”