1. Background Results Material and Methods Conclusions References
Biological activity screening of seven Plectranthus species: anticancer lead molecule search
Epole Ntungwe N.a, Joana Marçalo a, Catarina Garcia a, Catarina Reis a, Catarina Teodósio a, Carolina Oliveira a, Cláudia Oliveira a,
Amílcar Roberto a, Patrícia Rijo a,b*,
a CBIOS - Research Center for Biosciences & Health Technologies, U. Lusófona de Humanidades e Tecnologias, Campo
Grande 376, Lisboa,
b Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Lisboa, Portugal
P. cylindraceus
P. welwischii
P. sywernnertonii
P. ramosior
P. woodii
P. petiolaris
P. spicatus
Background
Results
Natural products are widely used as traditional medicines and are a common source of bioactive molecules for the treatment of bacterial infections. In particular, some plants of the genus Plectranthus (Lamiaceae) have demonstrated several applications, including the treatment of various infections [1]. According to the references of this study, scientific information on the analyzed spp. is scarce and with no phytochemical studies (except for Plectranthus cylindraceus). To the best of our knowledge, this is the first report comprising the evaluation of acetylcholinesterase inhibition, antioxidant and antimicrobial activities, as well as the Artemia salina lethality assay of the seven Plectranthus spp. acetonic extracts (P. swynnertonii, P. welwischii, P. woodii, P. cylindraceus, P. spicatus, P. ramosior and P. petiolaris).
Percentage yield:
Figure 1. Percentage yield (dry weight %w/w) of seven Plectranthus species
Acetylcholinesterase inhibition in vitro :
Material and Methods
Extraction: Acetonic extracts were obtained by sonication (10% w/v) [5] and their corresponding yields of extraction determined. Eqn. 1The extracts were then prepared at the concentration of 10 mg/mL in DMSO.
Acetylcholinesterase inhibition in vitro: All extracts were tested for their AChE inhibition [3] , and the inhibition percentage values were calculated according to the equations on Eqn. 2 and 3.
Antimicrobial activity: Well Diffusion Method: The antimicrobial activity was evaluated by measuring the diameter (mm) of the inhibition zone formed around the wells against two Gram-positive bacteria (E. faecalis and S. aureus), two Gram-negative bacteria (E. coli and P. aeruginosa) and two yeasts (S. cerevisiae and C. albicans) and compared to controls [2].
Antioxidant Activity (DPPH): The antioxidant activity of all extracts was measured by DPPH method [3]. Where AA is the antioxidant activity, ADPPH is the absorption of DPPH against the blank and Asample is the absorption of the extract. Eqn. 4
Brine shrimp lethality bioassay: In order to evaluate the toxicity of the differential extracts, a test of lethality to Artemia salina brine shrimp was performed and LC50 value of the most toxic determined [4]. Eqn. 5
(Eqn. 1). 2
Figure 2. Acetylcholinesterase percentage inhibition for seven Plectranthus species
at 1 mg/mL
Antimicrobial activity: Well Diffusion Method
Table 1. Antimicrobial activity of the acetonic extracts obtained by the well diffusion
method (mm). Extracts with inhibiton zone > 5mm were considered active
(Eqn. 2). 2
(Eqn. 3). 2
Antioxidant Activity (DPPH)
Eqn. 4. 2
Figure 3. Antioxidant activity of extracts under study tested at a concentration of 10 µg/mL
Brine shrimp lethality bioassay
Eqn. 5. 2
Conclusions
Figure 4.. Screening of seven Plectranthus spp. extracts for toxicity at a concentration of 10 ppm using the Artemia salina test
Of the seven Plectranthus species under study, P. ramosior acetonic extract had the highest percentage yield.
None of the extracts showed high acetylcholinesterase inhibition or antioxidant activities. Regardless, P. cylindraceus and P. ramosior revealed to be the best in these assays respectively.
Only P. ramosior acetonic extract showed positive results against the Gram-positive bacteria and yeast tested.
Three extracts were toxic against the brine shrimp, with P. swynnertonnii being the most toxic. P. ramosior is under further study as it displayed more biological activity than the rest of the extracts.
Table 2. LC50 values (mg/L) for the most active extracts using the Artemia salina test
References
[1] Lukhoba, C. W., et al., Plecctranthus: A review of ethnobotanical uses., 103:1–24, 2006Journal of Ethnopharmacology
[2] Rijo P, et al., Antimicrobial plant extracts encapsulated into polymeric beads for potential application on the skin. Polymers (Basel),6(2):479–90, 2014
[3] Rijo P, et al., Optimization of medicinal plant extraction methods and their encapsulation through extrusion technology. Measurement, 58:249–55, 2014
[4] Alanís-Garza BAet al., Screening of antifungal activity of plants from the northeast of Mexico. J Ethnopharmacol, 114(3):468–71, 2007
[5]Rijo P, et al., Screening of antioxidant and antimicrobial activities on Plectranthus spp. extract. Biomed Biopharm Res.;9(2):225–35.
4th Meeting of COST Action CM1407 Lisbon, September 2017)