α-Glucosidase inhibitory phenolics from Echeveria subrigida (B. L. Rob & Seaton) leaves.

Echeveria subrigida is native to Mexico and its methanol extract (ME) shows relevant biological activities for human health, including the α-glucosidase inhibitory (αGI) activity that suggests its antidiabetic potential. Fractionation of the ME based on the αGI activity (IC50 in µg/mL) showed that quercetin-3-O-ß-glucoside (131.1), isorhamnetin-3-O-ß-glucoside (166.4), and dimers to heptamers proanthocyanidins (9.6) were among the main responsible of αGI activity in the ME. The purified compounds showed better activity than acarbose (IC50 = 4426 µg/mL).

Transmission efficiency of tomato apex necrosis virus by Bemisia tabaci (Hemiptera: Aleyrodidae) biotype B in tomato.

Tomato apex necrosis virus (ToANV) is a new virus that causes important damage in tomato crops from the Culiacan Valley, Sinaloa, Mexico. To understand the relationship between ToANV and its vector Bermisia tabaci (Hemiptera: Aleyrodidae) (Gennadius) biotype B, laboratory and greenhouse trials were completed to: 1) determine the acquisition and inoculation access periods of ToANV by B. tabaci from tomato to tomato, 2) understand the transmission efficiency at different B. tabaci population densities, 3) estimate the time from inoculation of the virus at different B. tabaci densities to manifestation of symptoms in the plants, and 4) determine the retention time of the virus by the insect vector. The presence of the virus in plants was determined by reverse transcription-polymerase chain reaction amplification ofa 795-bp fragment (GenBank JN704068), which is phylogenetically related to ToANV (GenBank EF063242). The results showed that B. tabaci is an effective vector for ToANV with relatively long acquisition (12 h) and inoculation (9 h) access periods; a single adult is capable of transmitting and retaining the virus for up to 7d, suggesting a persistent mode of transmission. These results will help in the development of management strategies for controlling the vector and the disease.