Repellency and Toxicity of Selected Fractions, Identified Compounds and Blends of Commiphora africana Resin Against Bedbugs

Abstract

Bedbugs are blood-feeding arthropods that cause anemia in humans upon heavy feeding. Control measures are unsuccessful due to resistance to development, environmental pollution, and cost. There is a need to explore natural herbal-based phytochemicals to combat bedbugs. In this study, compounds from Comiphora africana resin were sequentially extracted, fractionated, identified, and evaluated against bedbugs as individual compounds and in combinations. The chemical constituents of the most active fraction were identified using Gas Chromatography-Mass Spectrometry. Results showed that the dichloromethane crude extract had the highest mean repellency (98.5% with an LC50 of 4.96 mg/L after 24 and 72 h of exposure time, respectively), similar to the positive control (neocidol). Column chromatographic separation of the dichloromethane extract yielded 9 fractions where “FR7” (eluted with 60% n-hexane in ethyl acetate) demonstrated the highest mean repellency of 79.0% with an LC50 of 10.12 mg/L after 2 and 24 h exposure times, respectively. From the identified compounds of FR7, cedrol had significantly ( P < .05) higher mean repellency (80.5%) after 6 h of exposure and toxicity (27.43 mg/L) after 24 h exposure. A six-constituent blend of compounds from FR7 [9-octadecenoic acid-ethyl-ester, octadecadien-1-ol, citronellyl formate, cedrol, n-hexadecanoic acid, (1,2)-dihydro-6-methoxy-naphthalene] had the highest mean repellency (93.4% after 12 h exposure) and toxicity (8.83 mg/L after 72 h exposure) than the other blends and individual compounds. This study reports fractions/compounds that can be used in bedbug control measures.

Exploring nature’s antidote: unveiling the inhibitory potential of selected medicinal plants from Kisumu, Kenya against venom from some snakes of medical significance in sub-Saharan Africa

“…Previous studies by Wanna, Karani, Anywar, Mwangi and their colleagues have shown that V. glabra was cytotoxic in A. salina (LC 50 = 658 μg/mL) (Wanna et al, 2023), W. ugandensis was non-cytotoxic in Vero cells (CC 50 of >250 μg/mL) (Karani et al, 2013) but cytotoxic to human glioblastoma cells (IC 50 = 7.6 μg/mL) (Anywar et al, 2022) and C. africana was cytotoxic to Vero cells (CC 50 > 20 μg/mL) (Mwangi et al, 2020). The compounds responsible for the toxicity of V. glabra and Z. usambarense have not been studied in detail but a study by Wairagu and colleagues established that cedrol, 9-octadecanoic acid-ethylester, octadecadien-1-ol, citronellyl formate, n-hexadecenoic acid, and 1,2-dihydro-6-methoxy-naphthalene isolated from the dichloromethane crude fraction of C. africana resin were toxic to bedbugs (Cimex lectularius) (Wairagu et al, 2022). Moreover, E-resveratol 3-O-rutinoside isolated from the methanol fraction of C. africana stem bark was highly cytotoxic to breast (MCF-7), liver (HepG2), lung (A549), and prostate (PC3) cancer cell lines (Segun et al, 2019).…”

Bio-active principles in Commiphora africana resin dichloromethane extract and their insecticidal activity against bed bugs

“…Sample collection: C. africana resin was harvested from mature trees in Taita Taveta County after identi cation and con rmation by a botanist from the National Museums of Kenya. The resin of the tree was harvested, packed and transported to KEFRI laboratory as previously reported by Wairagu [7]. C. africana resin was collected by making incisions in the stem bark with a sharp knife.…”

“…Adult bed bugs of mixed sexes were collected, reared and multiplied according to a protocol of Araujo [8] as brie y described by Wairagu [7]. In a glass cage (45 x 45 x 45 cm) partitioned into two sections, ve mice were introduced into one, and 100 bed bugs in the other.…”

“…A hundred grams (100 g) of powdered crude extract was subjected to separation with a column (100 cm long by 6 cm internal diameter) using Kieselgel silica gel 60G (70 -230 mesh). Silica gel (450 g) was rst packed in the separation column as was previously described by Wairagu [7] before introducing the extract on top of silica gel level. The crude extract was rst eluted with hexane and followed by a slow gradient of 0, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90 and 100% ethyl acetate in hexane.…”

“…resin in its crude form is locally used in control of bed bugs, lice, ticks and eas in various parts of Kenyan coastal region. In our previous study on evaluation of aqueous extract, polar organic solvent extracts, and non-polar organic solvent extracts of C. africana resin against bed bugs, we found that dichloromethane extract was the most potent repellent and toxic extract against bed bugs [7]. In this follow-up study, it is necessary to isolate pure compounds from the dichloromethane extract that are of biological importance against bed bugs.…”