<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mo stretchy="false">[</mml:mo><mml:mn>6</mml:mn><mml:mo stretchy="false">]</mml:mo></mml:math>-Shogaol Inhibits<i>α</i>-MSH-Induced Melanogenesis through the Acceleration of ERK and PI3K/Akt-Mediated MITF Degradation