Microwave irradiation enhances the in vitro antifungal activity of citrus by‐product aqueous extracts against Alternaria alternata

Abstract

Summary The effect of two lemon by‐product aqueous extracts at different concentrations (14, 7, 3.5 and 1 mg mL−1) was tested against the in vitro growth of Alternaria alternata. Prior to extraction, one batch of by‐product was dehydrated by freeze‐drying (untreated by‐product), while the other batch was treated by microwave irradiation in conjunction with freeze‐drying (microwave‐treated by‐product). High‐performance liquid chromatography (HPLC) was employed for the identification of individual phenolic compounds with potent antifungal activities. Both lemon by‐product aqueous extracts inhibited the mycelial growth and suppressed the spore germination of the fungus in a concentration‐dependent manner. In general, the extracts obtained from the microwave‐treated lemon by‐product displayed enhanced antifungal activity than those obtained from the untreated one. Scanning electron microscopy (SEM) revealed that both lemon by‐product extracts affected the hyphal morphology of the fungus. The antifungal activity of the extracts was attributed to their phenolic acid and ascorbic acid contents.

The Antifungal Activity of Gallic Acid and Its Derivatives against Alternaria solani, the Causal Agent of Tomato Early Blight

“…Moreover, numerous phenolic acids and phenolic-rich extracts exhibited high inhibitory effects on the radial growth of fungi [18,47]. Although considerable attempts have been made using naturally phenolic-rich products against Alternaria alternata [19][20][21][22][48][49][50][51], very few reports are available about their roles against A. solani. Nevertheless, the physiological and biochemical mechanisms behind this role are poorly understood.…”

Effect of drying techniques and operating conditions on the retention of color, phenolics, and antioxidant properties in dried lemon scented tea tree ( Leptospermum petersonii ) leaves

“…Previous research has shown several properties of plant derived phenolic compounds including antimicrobial (Bhuyan et al, 2017;Papoutsis et al, 2018), anti-inflammatory (Guo et al, 2014;Kazłowska et al, 2010), antioxidant (Papoutsis et al, 2017;Vuong et al, 2014), and bioactivities which lower the risk of cancer (Hsu et al, 2015;Ravishankar et al, 2013), cardiovascular diseases (Arts et al, 2001;Tangney & Rasmussen, 2013), and diabetes (Saravanan & Parimelazhagan, 2014;You et al, 2012). They can also help to boost up the immune system (Carlos et al, 2009;Reyes-Munguía et al, 2016).…”

Rapid detection and toxicity assessment of ochratoxin A by Photobacterium leiognathi in drinking water

“…The sterile saline severed as a blank control. The samples for SEM were fixed in 2.5% glutaraldehyde overnight, washed three times with 0.1 mol L À1 phosphate buffer for 10 min each time and then dehydrated in ethanol series (30%, 50%, 70%, 90% and 95%) for 20 min each time and finally in absolute ethanol for 1 h (Papoutsis et al, 2018). The specimens were dried at the automated critical point dryer (Leica EM CPD300; Microsystems GmbH, Wetzlar, Germany) and coated with gold using sputter coating for observation of cell morphological alterations under an Ultra 55 FEG SEM (Leo Electron microscopy, Zeiss, Oberkochen, Germany; Aleskerova et al, 2017).…”