Pheophytin Derived Near-Infrared-Light Responsive Carbon Dot Assembly as a New Phototheranotic Agent for Bioimaging and Photodynamic Therapy.

Carbon dots (CDs), a kind of phototheranostic agent with the capability of simultaneous bioimaging and phototherapy [i.e., photodynamic therapy (PDT) or photothermal therapy (PTT)], have received considerable attention because of their remarkable properties, including flexibility for surface modification, high biocompatibility, low toxicity and photo-induced activity for malignant tumor cells. Among numerous carbon sources, it has been found that natural biomass are good candidates for the preparation of CD phototheranostic agents. In this study, pheophytin, a type of Mg-free chlorophyll derivative and also a natural product with low toxicity, was used as a raw carbon source for the synthesis of CDs by using a microwave method. The obtained hydrophobic CDs exhibited a maximum near-infrared (NIR) emission peak at approximately 680 nm, and high singlet oxygen (1 O2 ) generation with a quantum yield of 0.62. The self-assembled CDs from the as-prepared CDs with DSPE-mPEG2000 retained efficient 1 O2 generation. The obtained carbon dot assembly was not only an efficient fluorescence (FL) imaging agent but also a smart PDT agent. Our studies indicated that the obtained hydrophilic CD assembly holds great potential as a new phototheranostic agent for cancer therapy. This work provides a new route for synthesis of CDs and proposes a readily available candidate for tumor treatment.

In vitro anti-diabetic activity of flavonoids and pheophytins from Allophylus cominia Sw . on PTP1B, DPPIV, alpha-glucosidase and alpha-amylase enzymes.

BACKGROUND: Ethno-botanical information from diabetic patients in Cuba led to the identification of Allophylus cominia as a possible source of new drugs for the treatment of type 2 diabetes mellitus (T2-DM). EXPERIMENTAL: Chemical characterization of the extracts from A. cominia was carried out using chromatographic and spectroscopic methods. The extracts were tested for their activity on PTP1B, DPPIV, α-glucosidase enzymes and α-amylase. RESULTS: The flavonoid rich fractions from A. cominia inhibited DPPIV enzyme (75.3±2.33%) at 30µg/ml and produced a concentration-dependent inhibition against DPPIV with a Ki value of 2.6µg/ml. At 30µg/ml, flavonoids and pheophytins extracts significantly inhibited PTP1B enzyme (100±2.6% and 68±1% respectively). The flavonoids, pheophytin A and pheophytin B fractions showed significant concentration-dependent inhibition against PTP1B with Ki values of 3µg/ml, 0.64µg/ml and 0.88µg/ml respectively. At 30µg/ml, the flavonoid fraction significantly inhibited α-glucosidase enzyme (86±0.3%) in a concentration-dependent pattern with a Ki value of 2µg/ml. None of the fractions showed significant effects on α-amylase. Fatty acids, tannins, pheophytins A and B, and a mixture of flavonoids were detected in the methanolic extract from A. cominia. The identified flavonoids were mearnsitrin, quercitrin, quercetin-3-alloside, and naringenin-7-glucoside. CONCLUSION: The pharmacological effects of the extracts from A. cominia earlier observed in experimental diabetic models was confirmed in this study. Thus a new drug or formulation for the treatment of T2-DM could be developed from A. cominia.